nervous system

controls the co-ordination of the body's organ systems, in close cooperation with the endocrine system.

(together nervous and endocrine maintain homeostasis)

• sensory functions (externally)
• integrating functions (within spinal cord)
• motor functions (externally)

• central nervous system
• peripheral nervous system

• brain
• spinal cord

• cranial nerves
• spinal nerves
• autonomic nerves
•   -sympathetic
•   -parasympathetic

neurons

(long, thin cells with branching processes at the ends, where they connect with other neurons)

• cell body/soma/perikaryon
• dendrites
• axons

• contains nucleus of cell
• contains majority of cell organelles that synthesize 

neurotransmitters

mitochondria

• areas containing large amounts of rough ER and ribosomes 
• stain darkly
• give grey coloration to the areas of the spinal cord that contain cell bodies of the neurons 

nissl bodies

extensions from cell body that receive stimuli/impulses from other neurons and convey this stimulation to the cell body.

may be modified into sensory receptors to receive or "sense" stimuli such as heat, cold, touch, pressure, stretch, or other physical changes from inside or outside the body.

• conducts impulses away from the cell body toward another neuron or other type of cell
• often covered in fatty substance called myelin

• fatty substance
• under microscope appears white (nervous tissues containing many myelinated axons referred to as white matter)

myelinated

speed

• (myelinated: goes fast
• non-myelinated: goes slow)

myelin

allow the nervous impulse to be transmitted to more than one other cell

support, structure, nutrition

• astrocytes
• oligodendrocytes
• microglia cells
• ependymal cells

• satelittle cells
• schwann cells

• neuroglial cell in CNS (look like stars)
• functions: 1. blood-brain barrier
• 2.support neurons by stabilizing from excessive movement and preventing damage to tissue
• 3. can change composition of interstitial fluid bathing the neurons

whats in blood cannot get in brain

• neuroglial cells in CNS
• function: line the axolemma (neurilemma on the axon) with a myelin sheath (myelinated) around every axon of CNS.
• composed of protein and phospholipids

neuro or neurilemma

• outer lining of the myelin:  neurolemma
• nerve lining: axolemma

lining of the neuron

terminal end of the nerve that does not touch the effector organ

point at which transmission occurs

(between neurons or between neuron and muscle fiber:neuromuscular junction)

99% of chemical transmissions in body

• neuroglial cell in CNS
• function: phagocytize in CNS (wander through and engulf&destroy cellular waste, debris, pathogens)

• neuroglial cells in CNS
• function: line the ventricles of the brain and spinal canal. responsible for circulation of cerebrospinal fluid that surrounds and protects brain and spinal cord. may also aid in production of spinal fluid

• neuroglial cells in PNS
• located in PNS with schwann cells
• function: surround clusters of cell bodies known as ganglia, insulating them from their surroundings

cluster of nerve cells responsible for surging impulses

(boots the power of the impulse as it comes through)

white matter

the cell membrane of specialized glial cells (fat cells) called oligodendrocytes in the brain and spinal cord&schwann cells in the nerves outside the brain and spinal cord.

small gaps between adjacent glial cells in the myelin sheath 

enhance the speed of conduction of the nervous impulses along the axon

• anaxonic neurons
• bipolar
• unipolar
• multipolar

all cell processes appear similar.

(there is no anatomical method differentiating between axons and dendrites)

2 processes arising from cell body in middle

(ear, eye, nose)

continuous dendritic and axonal process with the cell body lying off to one side

(generally have long axon, in PNS)

one axon from cell body with several dendrites coming in

(most common in CNS)

• sensory
• motor
• interneurons
• somatic sensory
• visceral sensory

• PNS
• afferent
• carry impulses from sensory receptors toward or into the CNS (carries impulses to spinal cord)

• PNS
• efferent
• carry impulses from the CNS to peripheral tissues, organs, or organ systems.

• situated between sensory and motor neurons
• found only in CNS

• impulse from muscle to CNS
• *minimal*

(neurons carry information from the external environment to CNS)

• impulse from organs to CNS
• *major*

(neurons carry information from w/in animals organs and other systems)

somatic sensory

visceral sensory

visceral (because involuntary)

• contains both afferent and efferent fibers
• may innervate several different organs, muscles, or glands

fibrous connective tissue that surrounds each axon

(located right on top of the nerve)

connective tissue that holds groups of axons in bundles

further held together by epinerium which also encloses a blood supply and fat deposits

(all to protect the framework of axons)

endonerium-->perinerium-->epinerium

study of the functioning of nervous tissue

changing the concentration of certain ion (Na, K) on the inside and outside of the membrane of the neuron

• K+ (Potassium)
• can move more easily out of the cell then Na+ can enter

(consequently there is a loss of positive charge from the inside of the cell, leaving the inside of the cell with a negative charge relative to the outside)

• outside the nerve
• high concentration of sodium ions (Na+) and chloride ions (Cl-)

high concentration of potassium ions (K+) and negatively charged proteins

there is an overall excess of negative charge on the inner surface of the membrane when compared to the outer surface.

(difference in distribution of positive&negative charges on either side of the cell membrane)

millivolts (mV)

resting neuron transmembrane potential: 0.07 V or -70mV

moves from higher concentration to lower concentration 

(the transport of K+ or Na+ does not require any input of energy=passive transport)

K+ moves out of the neuron and Na+ moves into the neuron normally without the sodium/potassium pump in a passive transport through the K+ and Na+ channels

strength of stimulus

both chemical and electrical forces combine to result in movement of ions into the cell.

• Na+ goes into the neuron because:
• -Na+ is at a higher concentration outside the cell than inside, the chemical gradient that exists results in movement into the cell
• -electrical attraction of positively charged ions (Na+) towards the negatively charged interior of the cell

Potassium

Sodium

Potassium and Sodium

must be able to retrieve some of lost K+ from outside the cell and get rid of excess Na+ from the inside of the cell

(to do this energy is used to activate sodium/potassium pump)

permits exchange of intracellular Na+ for extracellular K+

(by using a carrier protein molecule (like revolving door in nice hotels) located in the cell membrane, called the sodium/potassium ATPase pump)

carrier protein molecule that uses energy from the conversion of ATP (adenosine triphosphate) to ADP (adenosine diphosphate) to move the ions against their electrochemical gradients. This is active transport.

using energy to get done.

uses energy from conversion of ATP to ADP to move ions against their electrochemical gradient

takes energy in the form of active transport to move the Na+ ions out for the K+ ions that they move in

-70mV

• also referred to as resting potential
• cell membrane is polarized

alter transmembrane potential and reverse it momentarily so that the inside of the cell is positively charged and the outside negatively charged

change in potential

(depolarization&action potential basically same thing)

• 1. resting potential
• 2. nerve received stimulus
• 3. K+ moving out rapidly
• 4. no net charge movement (all Na+ & K+ outside)
• 5. Na+ moving in rapidly
• 6. repolarization

(1-5 all depolarization)

certain level/minimal amount of depolarization required before an action potential can be triggered

(once the stimulus has caused the neuron to become depolarized above the threshold level, then an action potential is triggered)

once threshold is exceeded, whether by gradual or sudden stimulus, the magnitude and duration of the response is the same

(muscles- contract to its fullest or not at all)

• neuron at this stage is unresponsive.
• if a second stimulus acts upon a neuron in which an action potential is on going then a second action potential will not be produced.

the time it takes for a neuron to be able to generate a second action potential from the start of the first

(time it takes to start another action potential)

period between the end of the absolute refractory period and a return to the resting potential

period where a second action potential can be triggered, although it requires the stimulus to exceed the threshold depolarization

sodium channels re-opened, influx of Na+ exceeds the movement of K+ leaving the cell, triggering a second action potential

action potential from the axon of the first nerve cell (presynaptic neuron) is carried across interstitial space (synaptic cleft) to the dendrites of the next nerve cell (postsynaptic neuron)

feel no pain

(give chemical to fill them up)

• synaptic gap/cleft is small.
• occurs when two cells are very close together

action potential is automatically transmitted into the adjacent cell by causing a membrane depolarization

• synaptic gap is large.
• impulse in the presynaptic neuron causes release of a chemical (neurotransmitter) which diffuses across the synaptic gap to the postsynaptic neuron and triggers a change in the membrane potential of the postsynaptic neuron. this depolarizes the postsynaptic neuron generating an action potential in the postsynaptic cell.

chemical means

most common: Acetylcholine

cholinergic

• nicotinic
• muscarinic

epi-nephrine

• amino acids
• monamines (modified amino acids)
• polypeptides
• acetylcholine
• nor-epinephrine
• some 20 compounds

• 1. Nor-epinephrine
• 2. Epinephrine
• 3. Dopamine
• 4. L-Dopa

adrenergic

• (cholinergic)
• "digestion"
• inhibitor=acetylcholinesterase
• two receptors: nicotinic&muscarinic

• (adrenergic)
• "fight"
• active only at post-synaptic site of sympathetic system
• four receptors: alpha 1, alpha 2, beta 1, beta 2 (all over the body)

• gama-aminobutyric acid (GABA)
• glutamate

• gama-aminobutyric acid (GABA)
• glutamate

• inhibitory neurotransmitter of CNS.
• binding GABA to its receptor produces hyperpolarization or inhibition.

• block external sounds
• as older decreases= "noisy"

• excitatory neurotransmitter of CNS.
• receptors for glutamate are involved with memory and learning.

infection of spinal cord and brain

T13 and L1

• makes sense because over abdominal area
• (always flows backward)

between last sacral and first coccygeal

• -usually clear, colorless, slightly alkaline fluid
• -contains small amount of protein
• -a few lymphocytes may be present but no RBC
• -circulates through 4 ventricles of the brain, only 3 produce the cerebral spinal fluid
• -also passes through subarachnoid space

function: protect the brain and spinal cord by forming a fluid cushion between the delicate nerve tissues and the bones of the skull and vertebral column

space between the inner (pia mater) and middle (arachnoid mater) of the 3 layers of connective tissue (meninges) which surround the brain

three layers of connective tissue that surround the brain

• 1. Pia mater
• 2. Arachnoid mater
• 3. Dura mater

lies on surface of spinal cord

(innermost layer of the meninges)

separated from the pia mater by the subarachnoid space via CSF

• outer layer
• thick membrane composed of tough fibrous tissue that lines the inside of the skull forming the periosteum

• opening between atlas and occipital
• very beginning of vertebral column starts here

(samples may be collected for analysis from an enlargement of the subarachnoid space here)

• pons
• medulla oblongata
• cerebellum

pons

pons and medulla oblongata 

controls motor coordination of the body

cauda equina

(group of nerves that run together in the region of the 7th lumbar vertebrae and the sacral region, resembling a mare's tail)

mixed 

6

passing through the intervertebral foramina, each passing into a different part of the body.

each spinal nerve surrounded by layer of meningeal dura and has a dorsal and ventral root.

carries sensory nerve fibers into the spinal cord

comprised of sensory afferent fibers

carries motor fibers to the musculoskeletal system

comprised of motor efferent fibers 

all other nervous tissue that is not within the brain or spinal cord.

(includes all the nerves that pass out from the spinal cord to muscles and organs, as well as those that carry impulses back into the CNS)

part of the PNS- Somatic Nerves supplying skeletal muscle

part of PNS- supplying smooth muscle, cardiac muscle, glands from the Autonomic System (all involuntary)

carry impulses from the CNS to skeletal muscles.

somatic sensory receptors are responsible for providing feedback to the brain from the skeletal muscle. majority of nerves in this system are under voluntary control.

cranial and spinal nerves

(depending upon the part of the body they innervate)

carry impulses to the brain like the sense of smell

(Olfactory)

carry impulses from the brain to the effector organ muscles of the eye

(Trochlear)

carry impulses from the brain to the effector organ and back to the brain.

(Trigeminal)

some cranial nerves "mixed" have both a motor and a sensory function

Trigeminal

spinal nerves

nerves interweave to produce a complex network of fibers

network of nerve fibers that gives rise to the radial, ulnar, and medial nerves supplying the forelimb

network of nerve fibers that gives rise to the sciatic (hip), obturator, perineal (area between anus and scrotum/vulva), pudendal (external genitals), and others.

tell you the depth of anesthesia 

inborn, involuntary response towards an external stimulus that is mediated by the nervous system

Pavlov's dogs

ex: reaction standing on a sharp object

• coughing
• swallowing
• vomiting
• salivation

• parasympathetic
• acetylcholine
• cholinergic

• sympathetic
• nor-epinephrine
• adrenergic

• palpebral (blink reflex)
• pedal
• ear flick
• corneal
• size of pupil
• pupillary light
• heart&respiratory
• response to surgical stimuli

• somatic sensory neurons (from muscles)
• visceral sensory neurons (from organs)

information about the external environment of the animal (from skin, muscles..)

the enteral environment and organs

stimulated by information from external environment such as touch, sight, smell, hearing, taste, pressure, temperature 

monitor movements and position of skeletal muscles and joints

(closed eyes open when loosing balance)

monitor internal environment such as respiratory, digestive, urinary, cardiovascular and reproductive

also stimulated by deep pressure and pain

• involved in detecting touch and painful stimuli
• located in the skin, muscles, viscera

• respond to touch and pressure
• located in dermis of skin

located in ear, eye, tastebuds

type of stimulus to which the receptor responds

detect chemical changes in local area around receptor. 

(chemoreceptors in brain detect changes in oxygen and carbon dioxide in blood)

respond to touch and pressure and are predominately located in the skin. 

there are also receptors that detect the degree of stretch of muscles in the stomach, lungs, blood vessels.

• baro receptors
• pressoreceptors
• mechanical receptors

• stimulated by changes in temperature
• located in the skin

• triggered by: stimulus that may cause tissue damage or injury
• release of chemicals in an area of inflammation

• stimulated by light
• found in retina of eye

collective term used to group together all the receptors that relay information about the position of the body and its movements

• receptors show a reduced response in the presence of a constant stimulus
• helps to prevent unnecessary waste of energy 

pain receptors or nociceptors 

(helps the survival of the animal bc as long as pain persists the animal will perform behaviors that minimize the pain/aids in healing process prevent from using injured site)

• controls parts of the body that are part of an animal's unconscious actions
• "involuntary"

(ex: when animal is anesthetized its heart still beats and breathing still occurs)

part of the nervous system where animal has some form of conscious control

• cardiovascular
• respiratory system
• digestive
• urinary
• reproductive system

• sympathetic (adrenergic)
• parasympathetic (cholinergic)

they have opposite effects: one being excitatory, one inhibitory

sympathetic portion of ANS

parasympathetic portion of ANS

• part of ANS that prepares the body for activity.
• "fight or flight"

preganglionic neurons in the thoracic and lumbar regions

• postganglionic neurons with which they synapse are located in 3 diff locations:
• sympathetic chain ganglia or lateral ganalia
• collateral ganglia
• adrenal medulla

• located on either side of vertebral column
• their neurons affect the head, body wall, limbs, inside of thorax

stimulation causes: constriction of blood vessels in skin,  increase blood to skeletal muscles&brain, release of lipid from fat stores, dilation of pupils, acceleration of heart rate and strength of cardiac contraction, bronchodilation

(instant)

• located anterior to bodies of vertebrae
• neurons affect tissue and organs of abdomen and pelvis

stimulation causes: reduced blood flow to visceral organs, decreased activity of digestive system, release of glucose from glycogen reserves in liver, reduction in rate of formation of urine, stimulation of release of lipids from fat stores

• center of each adrenal gland
• modified ganglion
• postganglionic neurons with very short axons which when stimulated release their neurotransmitters into blood stream
• not through a synapse but directly into circulation

allows the neurotransmitters (epinephrine&nor-epi) to have an effect as hormones on many target cells throughout the body

cholinergic synapses

excitatory

effectors

carry the impulses to the effector, and at the junction between the neuron and the effector another neurotransmitter is released. usually nor-epinephrine in which case we call the synaptic terminals adrenergic

alpha

alpha and beta

alpha 2 

• alpha 1
• (generally an excitatory effect)

inhibitory effect

• cause an increase in metabolism of cells
• (ex: increase in heart rate)

• tend to have inhibitory effect
• (ex: causing relaxation of smooth muscles in bronchioles)

4

(a1,a2,b1,b2)

2

(nicotinic, muscarinic)

• alpha 1
• beta 1
• beta 2

need to constrict vessels (vasoconstriction) and increase cardiac output

• bc shock is opposite.
• (shock is vasodilation and reduced cardiac output)

need to constrict vessels to: divert blood to area that needs it. constricting vessels raises the blood pressure which is the needed increased cardiac output.

• smooth muscle to:
• constrict blood vessels
• constrict sphincters in GI tract
• contract muscles to enlarge pupils
• contract sphincter of urethra

• cardiac muscle to:
• increase force of contraction of heart: increases cardiac output

• smooth muscle to:
• vasodilation of bronchi and lungs to allow for increased oxygen/ease breathing

• *DIGESTION*
• predominates when animal in relaxed state
• preganglionic neurons located in the brain (cranial ) and spinal cord (sacral)

Vagus nerve

anti-cholingergic drug

(anti-parasympathetic) 

• 9- Glossopharyngeal
• 10- Vagus

acetylcholine 

• nicotinic
• muscarinic

complementary 

(heart: if the sympathetic increases then the parasympathetic decreases

digestive: if sympathetic decreases, parasympathetic increases)

spleen and adrenal medullae have only one sympathetic innervation.

ciliary muscles of the eye are only innervated by the parasympathetic system.

parasympathetic system (pupil constriction)

miosis

sympathetic system (pupil dilation)

mydriasis

base level of activity that can increase or decreases depending on the situation

(ANS usually exists in a state of tone)

vagus nerve

(if severed, heart rate increases as the inhibiting effects of the parasympathetic nervous system are no longer present)

• spinal cord
• rapid

(levels of activity within the 2 divisions of ANS are controlled by areas within the brain and spinal cord)

• *cardiac
• *respiratory
• salivation
• digestive secretion
• movement of intestine
• urinary function

hypothalamus 

sympathetic 

("fight or flight")

• nor-epinephrine
• epinephrine
• dopamine
• L-dopa

• nicotinic
• muscarinic

supraspinatus and infraspinatus muscles

sensory

mixed

mixed

absolute refractory period

the cell is still refractory to stimuli of normal intensity but may respond to relatively large stimuli.

• heart rate
• force of heart contraction
• diameter of bronchioles (dilates)
• diameter of pupil (dilates)
• diameter of muscle blood vessels

• gastrointestinal motility, secretions, blood flow
• diameter of skin blood vessels
• diameter of blood vessels to kidney

gastrointestinal motility, secretions, and blood flow

• heart rate
• diameter of bronchioles (constricts)
• diameter of pupil (constricts)