lecture 4 Autonomic Nervous System

human physiology exam 1

impulse signals to the cell body. typically short, branched, and unmyelinated. make contact with other neurons

dendrites

impulses away from cell body. impulses from initial segment (trigger zone) side branches end in terminals. synaptic end bulbs

axons

what part of a neuron is the location for most protein synthesis

cell body

one direction only—away from cell body. movement at 1-5 mm per day

slow axonal flow

bidirectional, moves organelles and materials along surface of microtubules. 200-400 mm per day

fast axonal flow

sensory neurons

afferent

motor neurons

efferent 

interneurons

association

interneurons are what percent of total neurons

90%

…. connect neurons to neurons

interneurons

neuroglial cells make up what percentage of the volume of the central nervous system

50%

50 x more numerous than neurons, and smaller

neuroglial cells

True or false: neuroglial cells can undergo mitosis

true 

the 4 types of neuroglia cells in the central nervous system

oligodendrytes, astrocytes, microglia, and ependymal

the 2 types of neuroglia cells in the peripheral nervous system

schwann cells and satellite cells

star-shaped. form blood brain barrier, contain specialized end feet. metabolize neurotransmitters. regulate K+. provide structural support

Astrocytes

small cells found near blood vessels. defensive role/role in immune response. derived from precursor cells to macrophages and monocytes.

microglia

form the epithelial membrane lining cerebral cavities and the central canal. produce CSF

ependymal cells

surround cell bodies in peripheral ganglia. support neurons in PNS ganglia

satellite cells

most common. each forms myelin sheath around more than one axon in the CNS. Analogous to Schwann cells of the PNS

oligodendrocytes

a multilayered lipid and protein covering

myelin sheath

what 2 things does myelination do

1. Electrically insulates the axon and 2. increases speed of nerve impulse conduction

the cytoplasm and nucleus of a schwann cell

neurilemma

gaps in myelin

nodes of ranvier

myelinated fibers appear what color

white

unmyelinated fibers in the PNS are only surrounded by 

neurilemma 

produce the myelin that covers the axons in the PNS. they encircle PNS axons

schwann cells 

Functions of the ANS

contributes to homeostasis by responding to subconscious visceral sensations and exciting or inhibiting smooth muscle, cardiac muscle, and many glands 

Components of the ANS

autonomic sensory neurons, integrating centers in the CNS, and autonomic motor neurons

specialized network of nerves and ganglia forming an independent nerve network within the wall of the GI tract

enteric division

Most significant difference between ANS and SNS

involvement of conscious control 

In this nervous system, feedback via tactile, thermal, pain and proprioceptive sensations are consciously percieved, and skeletal muscle is the main tool used to provide reflexive and voluntary movement

SNS

Even though we are not generally conscious of breathing, the muscles that generate respiratory movements are

skeletal muscles, controlled by somatic motor neurons

True or false: if a somatic motor neuron ceases to stimulate a muscle, the result is a paralyzed, limp muscle that has no tone

true 

This nervous system usually operates without conscious control, though centers in the hypothalamus and brain do provide regulation for reflexes

ANS

sensory receptors located in blood vessels, visceral organs, muscles, and the nervous system that monitor conditions in the internal environment

interoceptors

examples of interoceptors 

chemoreceptors that monitor blood CO2 level, mechanoreceptors that detect the degree of stretch in the walls of organs or blood vessels 

regulate visceral activities by either increasing (exciting) or decreasing (inhibiting) ongoing activities in their effector tissues

autonomic motor neurons

often the basis for polygraph tests, as they cannot be consciously altered

autonomic responses

Sensory input for SNS

from somatic senses and special senses 

Sensory input for ANS

mainly from interoceptors, some from somatic and special senses

control of motor output for SNS

voluntary control from cerebral cortex, with contributions from the basal ganglia, cerebellum, brain stem, and spinal cord

control of motor output for ANS

involuntary control from hypothalamus, limbic system, brain stem and spinal cord. limited control from cerebral cortex

motor neuron pathway of the SNS

one neuron pathway, somatic motor neurons extending from CNS synaspe directly with effector

motor neuron pathway of the ANS

usually 2 neuron pathway. preganglionic neurons extending from CNS synaspe with postganglionic neurons in autonomic ganglion, and postganglionic neurons extending from ganglion synaspe with visceral effector.

Neurotransmitters and hormones of the SNS

all somatic motor neurons release ACh

Neurotransmitters of the ANS

All sympathetic and parasympethetic preganglionic neurons release ACh. Most sympathetic postganglionic neurons release norepinephrine; those to the sweat glands release ACh. All parasympathetic postganglionic neurons release ACh. 

Effectors of the SNS

skeletal muscle

Effectors of the ANS

Smooth muscle, cardiac muscle, glands

Responses of the SNS

contraction of skeletal muscle

responses of the autonomic nervous system

contraction or relaxation of smooth muscle, increased of decreased rate and force of contraction of cardiac muscle, increased or decreased secretions from glands

thoracolumbar

sympathetic division

craniosacral

parasympathetic division

ANS division with nerves that exit from the spinal cord

sympathetic

ANS division with nerves that exit from the cranium

parasympathetic

The only effector organs where the parasympathetic nerves that connect to it exit from the spine

genitals, uterus, urinary bladder, ureter

how many neurotransmitters are used in the ANS

2

synaspes that use ACh

cholinergic

Synaspes that use norepinephrine

adrenergic 

2 types of cholinereic receptors

nicotinic and muscarinic

these cholinergic receptors are found in the ganglia

nicotinic

these cholinergic receptors are found at the synapses with effector organs

muscarinic

the neurotransmitter used at most sympathetic postganglionic synapses

norepinephrine

the one effector organ where ACh is used at the sympathetic postganglionic synaspe 

sweat glands

the neurotransmitter used at all parasympathetic postganglionic synaspes

ACh

true or false: only nicotinic receptors are used at the preganglionic neuron both both sympathetic and parasympethetic

true

true or false: at the effector organ, muscarnic receptors are used for postganglionic parasympethic ganglion, and adrenergic receptors are used for postganglionic sympethetic ganglion

true

true or false: ACh is used at all the synaspes of sympathetic and parasympathetic ganglia. 

true 

If you activate nicotinic receptors, you only get

excitation

if you activate muscarinic receptors, you get either

excitation or inhibition

these receptors are found on the dendrites and cell bodies of all ANS cells 

nicotinic

these are found on the plasma membranes of all parasympathetic effectors

muscarinic receptors

adrenergic receptors either

excite or inhibit

these inactivate norepinephrine

MAO, COMT 

adrenergic receptors that excite

Alpha 1 and beta 1

adrenergic receptors that inhibit

Alpha 2 and Beta 2

what does the beta 3 adrenergic receptor do 

increases thermogensis in brown fat

True or false: the effects of adrenergic neurons are longer lasting than those of cholinergic neurons

true

binds to and excites a receptor, mimicking the effect of a natural neurotransmitter or hormone

agonist

binds to and inhibits a receptor, prevents action of natural neurotransmitter or hormone

anatagonist

agonists or antagonists to selectively activate or block ANS receptors

drugs

excessive sympathetic stimulation of smooth muscle in the arterioles of the digits; digits become ischemic after exposure to cold or with emotional stress

raynaud’s syndrome

exaggerated response of sympathetic NS in cases of spinal cord injury above T6

autonomic dysreflexia