Autonomic Nervous System

Download Report

Transcript Autonomic Nervous System

Autonomic Nervous System
• Controls automatic
functions at
subconscious level
• ______________ nervous
system - nerves emerge
from thoracic and lumbar
vertebral regions
(thoracolumbar system)
• Thoracic nerves 1-13,
Lumbar nerve 1
• ____________________
nervous system - nerves
emerge from brain and
sacrum (cranial-sacral)
• Cranial nerves 3, 7, 9, 10;
Sacral nerves 2,
3, 4
Table 13-3. Effects of Sympathetic and Parasympathetic Nervous
Sympathetic System
Parasympathetic System
Heart rate
Force of heart contraction
No significant effect
Diameter of bronchioles
Increases (dilates)
Decreases (constricts)
Diameter of pupil
Increases (dilates)
Decreases (constricts)
GI motility, secretions,and blood flow
Diameter of skin blood vessels
No significant effect
Diameter of muscle blood vessels
No significant effect
Diameter of blood vessels to kidney
No significant effect
Neurotransmitters and Receptors
• Sympathetic nervous system
• 1º neurotransmitter—_____________________
• Released from Sympathetic POSTganglionic neurons
• ADRENERGIC neurons - neurons that release norepinephrine
• Epinephrine/norepinephrine also released from adrenal medulla
• To elicit an effect, effector organ must contain receptor for epi/norepi
Neurotransmitters and Receptors
1. ______- adrenergic receptors – cause vasoconstriction of skin,
GI tract, and kidney (don’t need to digest, make urine, or bleed
2. _______-adrenergic receptors - increase heart rate and force of
3.________-adrenergic receptors - cause bronchodilation
Neurotransmitters and Receptors
• Parasympathetic nervous system
• 1º neurotransmitter—__________________
• CHOLENERGIC neurons - release acetylcholine
• (Even though norepinephrine is the neurotransmitter associated with the
sympathetic nervous system, the PREganglionic neuron in BOTH the
Sympathetic and Parasympathetic systems is a CHOLINERGIC neuron that
• 2 types:
• Nicotinic receptors- found on POSTganglionic neurons in BOTH the
Sympathetic and Parasympathetic systems
• Muscarinic receptors- found on the target organs and tissues supplied by the
postganglionic neuron of the parasympathetic nervous system
Summary: receptor types
Reflexes are rapid, automatic responses to stimuli. They
serve to protect the body and maintain homeostasis
• ____________ reflexes - involve contraction of skeletal muscles
• _______________ reflexes - regulate smooth muscle, cardiac
muscle, and endocrine glands
• _______________ reflex - stimulus and response are on same
side of body
• ________________ reflex - starts on one side of body and
travels to opposite side
Reflex Arc
5 Components:
Sensory receptor—activated by stimulus
Sensory neuron—transports AP to gray matter of spinal cord or brain stem
(cranial n.) and synapses with other neurons
Interneuron—sensory info integrated with info from other sensory neurons
Motor Neuron—response is sent out via motor neuron
Target organ—effector cell
Stretch Reflex (tap knee)
• Monosynaptic (1) reflex arc; ipsilateral reflex
• Involves 1 sensory neuron and 1 motor neuron
• Signals also sent to:
• Antagonistic muscle (inhibitory)
• Cerebellum/Cerebrum
Withdrawal Reflex
• Also called flexor reflex; ipsilateral reflex
• Several interneuron synapses
• Several segments of spinal cord
• Results in:
• Contraction of muscles
• Before cerebrum is aware
• Inhibition of antagonist muscles
Crossed Extensor Reflex
• Contralateral reflex
• Withdrawal reflex initiated
• Afferent sensory neuron synapses with
• Causes contraction of opposite extensor
CNS Moderation of Reflexes
• Upper CNS (brain) normally produces an inhibitory
effect on the reflex arcs (muffled effect)
• With injury, intact reflex arcs caudal to spinal cord trauma
become __________________
• Trauma to a portion of the reflex arc results in either
______________ or absent reflexes