phys-HEENT 1

• 31
• 12

• Sensory -  gathers info
• Integrative - information is brought together
• Motor - responds to signals, homeostasis

structure and function

• Afferent neurons:
• --Inform CNS about conditions in both the external and internal environment
• --At its peripheral ending, there is a Sensory Receptor that generates Action Potentials in response to stimulus
• Efferent neurons:
• --Carry instructions from CNS to effector organs – muscles and glands
• --Lie primarily in PNS

• Found entirely within CNS
• Lie between Afferent and Efferent neurons
• Responsible for:
• ---Integrating afferent information and formulating an efferent response
• ---Interconnections between interneurons are responsible for higher mental functions associated with the “mind”

• Soma or cell body: contains nucleus &   machinery of cell 
• Dendrites: receive messages from other neurons  and conduct electrical impulses toward the cell body 
• Axon: is the long tubelike portion of the neuron   that   carries information away  from the cell body. It is the   conductive part of the neuron.

Glia

• glial cells
• they do not initiate or conduct nerve impulses
• do communicate with neurons and among themselves via chemical signals
• serves as connective tissue of CNS physically, metabolically, & functionally support interneurons
• astrocytes, oligodendrocytes, microglia, ependymal cells

• Named for starlike shape (astro = “star”)
• Most abundant glial cells
• Main “glue” of CNS – holds neurons together
• Guide neurons during fetal brain
• development
• Induce capillaries of brain to undergo changes that aid in establishment of blood-brain barrier
• Important in repair of brain injuries and in neural scar formation
• Play role in neurotransmitter activity
• ---Take up and degrade Glutamate and GABA
• Take up excess K+ from brain ECF
• ---Helps maintain optimal ion conditions for neural excitability
• Along with other glial cells – enhance synapse formation and modify synaptic transmission

Form myelin sheaths around axons in CNS

• Immune defense cells of the CNS
• In resting state release low levels of growth factors that help neurons and other glial cells survive and thrive
• ---Nerve Growth Factor = helps neurons and glial cells survive

• Line internal, fluid-filled cavities of the CNS
• In ventricles of brain, help form and circulate cerebrospinal fluid

dendrite --> cell body ---> along axon ---> synapse (gap)

NT

• the meninges.
• 1. dura mater
• 2. arachnoid mater
• 3. pia mater

dura mater on top

cerebrospinal fluid (CSF)

• protect the brain
• form supporting framework
• enclose fluid-filled cavity: subarachnoid space

• MF: Serves as a shock-absorbing fluid to prevent brain from bumping against hard skull
• other functions:
• Exchange of materials between neural cells and interstitial fluid surrounding brain
• Formed primarily by choroid plexuses
• Richly vascularized masses of pia matter tissue that dip into pockets formed by ependymal cells
• CSF forms as a result of selective transport mechanisms across membranes of choroid plexuses

• Protects brain from chemical fluctuations in blood
• --Strictly limits exchange between blood and brain
• Minimizes possibility that harmful blood-borne substances might reach central nervous tissue
• Prevents certain circulating hormones that could also act as neurotransmitters from reaching brain
• Limits use of drugs for treatment of brain and spinal cord disorders
• --Many drugs cannot penetrate BBB

• Subconsciously regulate your internal environment by neural means
• Experience emotions
• Voluntarily control your movements
• Be consciously aware of your own body and your surroundings
• Engage in other higher cognitive processes such as thought and memory

• forebrain
• cerebellum
• brain stem

• cerebrum
• --basal nuclei
• --cerebral cortex
• Diencephalon
• --hypothalamus
• --thalamus

• highly developed
• 80%
• 2, corpus callosum
• (2 halves= R and L hemispheres)
• basal nuclei
• highly convoluted cerebral cortex

• gray matter
• white matter
• occipital, temporal, parietal, frontal

• frontal: reasoning, thinking, language
• -3 main functions:
• ---- voluntary motor acitivity
• ---- speaking ability
• ---- elaboration of thought
• parietal: touch, pain, relation of body parts (somatosensory), Receive and process sensory input, Somatosensory processing
• temporal: hearing, Initial reception of auditory (sound) sensation
• occipital: vision, Carries out initial processing of visual input

• Located in frontal lobe
• Confers voluntary control over movement produced by skeletal muscles
• Primarily controls muscles on the opposite side of the body
• Motor homunculus
• -Depicts location and relative amount of motor cortex devoted to output to muscles of each body part

• Plays preparatory role in programming complex sequences of movement
• Complex patterns of movement:
• --Opening or closing hand

Important in orienting the body and arms toward a specific target

• Lies posterior to primary somatosensory cortex
• When either of these areas is damaged, one can’t process complex sensory information to accomplish purposeful movement
• ---ie: manipulating eating utensils

• Broca's area
• -- governs speaking ability
• Wernicke's area
• --Concerned with language comprehension
• --Responsible for formulating coherent patterns of speech

strokes

• defect in mechanical aspect of speech
• Weakness or incoordination of muscles controlling vocal apparatus

• Excels in logical, analytic, sequential, and verbal tasks
• --Math, language forms, philosophy
• Tends to process information in fine-detail way

• Excels in nonlanguage skills
• --Spatial perception and artistic and musical talents 
• Views the world in a big-picture, holistic way

Associated with “thinkers”

“creators”

• Inhibiting muscle tone throughout the body
• --Inhibitory role in motor control
• Selecting and maintaining purposeful motor activity while suppressing useless or unwanted patterns of movement
• Helping monitor and coordinate slow, sustained contractions, especially those related to posture and support

• hypothalamus
• thalamus

direct regulation of internal environment

• Controls body temperature
• Controls thirst and urine output
• Controls food intake
• Controls anterior pituitary hormone secretion
• Produces posterior pituitary hormones
• Controls uterine contractions and milk ejection
• Serves as a major ANS coordinating center
• Plays role in emotional and behavioral patterns
• Participates in sleep-wake cycle

• Positively reinforces voluntary motor behavior initiated by cortex
• Part of diencephalon
• Serves as “relay station” and synaptic integrating center for processing sensory input on its way to cerebral cortex
• Along with brain stem and cortical
• association areas, important in ability to direct attention to stimuli of
• interest
• Capable of crude awareness of various types of sensation but cannot distinguish their location or intensity

• Not a separate structure but a ring of forebrain structures that surround the brain stem
• Includes portions of the hypothalamus

• Emotion
• Basic, inborn behavioral patterns related to survival and perpetuation of the species
• Plays important role in motivation and learning

• Storage of acquired knowledge for later recall
• Memory trace
• --Neural change responsible for retention or storage of knowledge
• Short-term memory
• --Lasts for seconds to hours
• Long-term memory
• --Retained for days to years
• Consolidation
• --Process of transferring and fixing short-term memory traces into long-term memory stores
• Working memory
• --Temporarily holds and interrelates various pieces of information relevant to a current mental task

• Subcortical region of the brain
• Attached at top rear portion of brain stem
• Important role in planning, initiating, and timing movements by sending input to the motor areas of cortex
• Maintains proper position of the body in space
• Subconscious coordination of motor activity (movement)
• Plays key role in learning skilled motor tasks

balance and in planning and executing voluntary movement

• Continuous with spinal cord
• Controls many life-sustaining processes, such as respiration, circulation, and digestion
• Concerned with maintaining proper position of the body in space and subconscious coordination of motor activity (movement)
• All incoming and outgoing fibers traversing between periphery and higher brain centers must pass Brain Stem
• Consists of:
• ---Midbrain
• ---Pons
• ---Medulla

• Most of cranial nerves arise from brain stem
• Neuronal clusters within brain stem control heart and blood vessel function, respiration, and many digestive functions
• Plays role in regulating muscle reflexes involved in equilibrium and posture
• Reticular formation within brain stem receives and integrates all incoming sensory synaptic input
• Centers that govern sleep are in brain stem (evidence suggests center promoting slow-wave sleep lies in hypothalamus)

• Slow-wave sleep
• Paradoxical, or REM sleep

Sensory perception; voluntary control of movement; language; personality traits; thinking, memory, decision making, creativity, self-consciousness

Inhibition of muscle tone; coordination of slow, sustained movements, suppression of useless patterns of movement

Relay station for all synaptic input; crude awareness of sensation; some degree of consciousness; role in motor control

Regulation of many homeostatic mechanisms, such as temperature control, thirst, urine output, food intake; important link between nervous & endocrine systems; role in sleep-wake cycle; role in emotion & basic behavioral patterns

Origin of majority of peripheral cranial nerves; CV, respiratory & digestive control center; regulation of muscle reflexes involved with equilibrium & posture; role in sleep-wake cycle; reception & integration of all synaptic input from spinal cord; arousal & activation of cerebral cortex

• Neuronal link between brain and PNS
• Integrating center for spinal reflexes

• named for the region of vertebral column from which they emerge.
• 8 pairs cervical (neck) nerves
• 12 pairs thoracic (chest) nerves
• 5 pairs lumbar (abdominal) nerves
• 5 pairs sacral (pelvic) nerves
• 1 pair coccygeal (tailbone) nerves

• Simple, or basic, reflexes
• -Built-in, unlearned responses
• ---ie: pulling your hand away from a burning hot object
• Acquired, or conditioned, reflexes
• -Result of practice and learning
• ---ie: pianist striking a particular key on seeing a given note on the music staff

• Neural pathway involved in accomplishing reflex activity
• 5 basic components:
• -Receptor
• -Afferent pathway
• -Integrating center
• -Efferent pathway
• -Effector