BIOL121: 05/28-29/26 (Mendel)

sensory input

gather info about internal and external environments

types of receptors

PHOTORECEPTOR = in retina, detect light and convert to nerve signals for vision

THERMORECEPTOR = detects changes in temperature

MECHANORECEPTOR = responds to physical senses (touch, pressure, vibration, stretch, sound)

NOCICEPTOR = pain receptor detecting tissue damage or harmful stimuli

PROPRIORECEPTOR = found in muscle, tendons, joints detecting body position and movement

integration

processing/interpretation of sensory information by the nervous system to determine a response

motor output

response to processed sensory info by sending signals to effectors to product an action

CNS

brain and spinal cord

act as body’s control center by receiving sensory input, processing info, directing motor output

PNS

all nerves outside brain and spinal cord (connect CNS to body)

carries sensory info to CNS, motor commands from CNS to muscle and glands

sensory afferent

part of PNS that carries sensory info from receptors to CNS

detect stimuli and sends info to CNS for processing

almost all are unipolar

cell bodies located in ganglia in PNS

somatic sensory receptor

detect stimuli from the skin, skeletal muscles, joints, body wall (voluntary)

visceral sensory receptors

detect stimuli from internal organs, stomach, bladder, blood vessels, lungs

motor efferent

part of PNS that carries commands from CNS to muscles and glands (effectors)

multipolar

most cell bodies are located in CNS (except some autonomic neurons)

autonomic nervous system (ANS)

division of motor nervous system

controls involuntary functions of cardiac muscle, smooth muscle, glands

sympathetic

part of ANS that prepares body for fight or flight situations

increase HR, dilate pupils, increase breathing, inhibit digestion

parasympathetic

part of ANS promoting rest and digest (conserve energy/homeostasis)

slows HR, constrict pupils, stimulate digestion, conserve energy

neurons (nerve cells)

excitable cells transmitting electrical signals (nerve impulses)

neuroglia (glial cells)

support cells surrounding delicate neurons

maintain environment for neurons to function properly

astrocytes

CNS glial cell that support and brace neurons, wrap around capillaries forming blood-brain barrier

alcohol, drugs, nicotine, medication pass through blood-brain barrier

microglial

phagocytic glial cells of CNS that remove pathogens, dead cells and debris

small, ovoid cells with thorny processes, migrate toward injured neurons, cleanup like WBC

ependymal

ciliated glial cells that line the ventricles of the brain and central canal of spinal cord

form permeable barrier between cerebrospinal fluid (epidemal cell)

oligodendrocytes

CNS glial cells that form the myelin sheath around axons

insulate axons and increase speed of nerve impulse

studded with growth inhibiting enzymes

satellite cells

glial cells in PNS surrounding neuron cell bodies and regulate chemical environment around neurons

schwann cell

glial cells in PNS that form myelin sheath in thicker nerve fibers

vital to regeneration of damaged peripheral nerve fibers

increase speed of neurological transmission

gray matter

store memory, thinking, decision making

neuron cell bodies, dendrites, unmyelinated axons (slower)

white matter

region of nervous system composed mainly of myelinated axons (fast)

carry nerve impulses between different areas of CNS

neuron

structural unit of nervous system

highly specialized cells conducting impulses

lifelong, amniotic, high metabolic rate (O2, glucose supply)

cell body with 1+ processes

axon hillock

cone shaped region where the cell body meets the axon, move one way away from cell body

site where action potentials are initiated, end terminal releases neurotransmitters

ganglia

clusters of neuron cell bodies located in the PNS

relay and process info outside of CNS (sensory)

nuclei

clusters of neuron cell bodies located in the CNS

process and integrate info within brain and spinal cord (motor)

dendrites

branched neuron processes that receive signals and carry them toward cell body as graded potentials (short distance signals)

input region of neuron

axon

long neuron process that carries nerve impulses away from the cell body along AXOLEMMA to AXON TERMINAL which secretes NEUROTRANSMITTERS

NERVE FIBERS = long axons

AXON COLLATERALS = occasional branches

TRACTS = bundles of axons in CNS (cannot regenerate, Oligodendrocyte)

NERVES = bundles of axons in PNS (can regeneration, Schwann)

myelin sheath

protect and electrically insulate axon

increases speed of nerve impulse transmission

myelinated fibers

axons surrounded by a myelin sheath

conducts nerve impulses rapidly

nonmyelinated fibers

axons lacking myelin sheath

conduct nerve impulses more slowly

myelin sheath gap (nodes of ranvier)

gaps between adjacent Schwann cells (myelin sheath segments) along an axon

allow action potentials to “jump” from node to node (saltatory conduction), voltage-gated ion channels (Na), increase conduction speed

myelin sheaths in CNS

insulating coverings around axons formed by oligodendrocytes

increase speed of nerve impulse conduction

each cell can wrap up to 60 axons at a time

multipolar neuron

motor efferent neuron and integration (stop and thinking) carrying commands from CNS to effector

cell bodies are in brain or spinal cord

neuron with 1 axon + many dendrites, most common neuron type, 3+ processes

bipolar neuron

neuron with 1 axon + 1 dendrite

associated with special senses such as vision, smell, hearing

unipolar neuron

sensory afferent neuron carrying info to CNS

PERIPHERAL = impulses from sensory receptor toward cell body

CENTRAL PROCESS = impulses from cell body into CNS

cell bodies sensory nerve in DORSAL ROOT GANGIAL PNS

interneurons

shuttle signals through CNS pathways

99% of body’s neurons (between motor and sensory neurons)

action potential

begins at AXON HILLOCK

Na-K PUMP: 3 Na+ OUT, 2 K+ IN (K+ leaks out)

ALL OR NONE PRINCIPLE = 15mV worth of stimulation MUST be at -55mV (threshold) for stimulation

AXON TERMINAL = release ACh to open Na+ door

DEPOLARIZATION = Na+ rushed inside cell (-70mV —> +30mV)

ACTION POTENTIAL = Na+ channel close, K+ channel open (+30mV)

ABSOLUTE REFRACTORY PERIOD = potential cannot go up

REPOLARIZATION = K+ channel opens (+30mV —> -90mV)

Na-K PUMP ON = tuned back on to go back to -70mV (-90mv —> -70mV)

BUMP = less action potential

PUNCH = more action potential

axonal terminal

releases ACh (stimulus released, signal saying “go”)

cause patch of sarcolemma to become permeable to Na+ (sodium channels open)

open “door” one direction = DEPOLARIZATION (less negatively charged)

Na+ enters cells and resting potential is decreased (-55mV)

action potential started if stimulus strong enough

myelination in PNS

formed by Schwann cells

wraps around axon in jelly roll fashion

one cell forms one segment of myelin sheath

axon plasma membrane have less protein, no channels or carriers = good electrical insulators