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What are the three types of cell to cell communication and the qualities of each?
1. Neurotransmitters: rapid, specific, direct
2. Local mediators: paracrine, intermediate, released into interstitium
3. Hormones: endocrine, released into circulation, slow, diverse actions
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Can neurons divide? Why?
No, because they are too specialized
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What is special about neurons in relation to metabolism?
They use facilitated transport to obtain glucose...but independently of insulin.
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Signal transduction order in neurons.
- 1. Signal received in dendrites
- 2. Travel to axo hillock (Site of AP generation)
- 3. Travel down axon to synapse
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What kind of cells work via AP mechanisms?
- 1.Neuronal
- 2.Muscle
- 3.Cardiac
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What kind of synapses do most neurons employ?
1. Chemical, unidirectional synapses
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Unique distinction of vertebrates?
Only vertebrates have MYLENATED axons!
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Where do sensory and motor neurons lie in the spinal cord?
Sensory neurons: dorsally
Motor/somatic NS neurons: ventrally
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What is the autonomic NS regulated by?
The hypothalamus
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ACh receptors
a) Found ALL throughout the PNS except for sympathetic neuroeffector synapses
b) Nicotinic: muscles
c) Muscarinic: found in the parasympathetic NS
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What is the major role of sensory receptors?
Transduction of physical stimuli to neural stimuli
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What kind of lens is the eye?
Converging ; objects behind focal point are REAL and INVERTED
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What effect do the contraction/relaxation of ciliary muscles have on the lens and focal point?
Contraction: Bends the lens, makes more spherical, moves focal point CLOSER to lens
Relaxation: straightens lens, flattens, moves focal point AWAY from lens, harder to see closer objects, happens in old age when muscles tire
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What kind of photoreceptors does the fovea contain?
Only cones
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Cornea
First place light hits the eye ; nonvascular and made of collagen ; where most bending of light occurs because it is highly refractive
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Path of light
Iris/Pupil --> Cornea --> Aqueous humor --> Lens --> Vitreous humor --> Retina
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Path of sound
Pinna (outer) --> Tympanic mem. (middle) --> Malleus, incus, stapes --> Cochlea (stereocilia + Organ of Corti)
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Where is sound transduced?
By the hair cells of the Organ of Corti in the Cochlea
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Lever system in the ear?
Malleus, Incus, and Stapes are 3 small bones acting as levers.
Their displacement from sound is small, making the force from sound much larger and more easily transduced.
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Semicircular canals
Important in vestibular information
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Somatic vs. Autonomic NS
Somatic NS is in control of SKELETAL MUSCLES
Autonomic is in control of smooth and cardiac muscles !
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What NS control simple reflex arcs?
Somatic
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What controls shivering?
Somatic NS because shivering involves the contraction of skeletal muscles to generate heat
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Sweating is controlled by...?
Autonomic NS (both branches)
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ACh actions on heart?
Acts via vagus nerve to increase time between contractions, slowing down HR
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Acclimatization
Endocrine system because it happens over time
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By which cells is the myelin sheath made in the CNS and the PNS?
CNS = Oligodendrocytes
PNS = Schwaan Cells
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Why is the membrane potential negative?
3Na+ out, 2K+ in
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What makes testosterone?
Adrenal glands
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What makes estrogen?
ovaries
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Reflex arcs
Involve CNA - but also involve both the excitation and inhibition of muscle groups.
Remember that they involve CNA because they go through the spinal cord!
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