Download AUTONOMIC NERVOUS SYSTEM

AUTONOMIC NERVOUS
SYSTEM
The ANS is part of the efferent
portion of the peripheral nervous
system
Functions
 Regulation
of heartbeat
 Smooth muscle contraction
 Secretions of glands
***It is controlled by the hypothalamus
with input from the cerebral cortex and
limbic system
Comparing the Somatic and
Autonomic Nervous System
Somatic Nervous System
Receptors (sensory neurons) are sensitive to
external enviroment and transmit signals to the
CNS
 Causes stimulation of reflexes or conscious
sensation
 Information from efferent fibers sent to skeletal
muscle
 Cell bodies located in CNS; only one motor
neuron involved

Autonomic Nervous System
Internal enviroment
monitored by
interoceptors
 Stimulation of ANS
rarely results in
conscious sensations
 Visceral Effectors:
smooth,cardiac muscle
and glands


Pathway involves TWO
motor neurons in
sequence
–

Preganglionic neuron cell
body is in CNS;
Postganglionic cell body is
outside CNS
Axon fibers of 2nd
neuron not myelinated
and release ACh or NE
Divisions of the Autonmic
Nervous System
Sympathetic Division - Flight or Fight
Parasympathetic Division - Rest or Repose
Differ in location of
preganglionic cell body
 Sympathetic
Division (Thoracolumbar) cell bodies located in lateral gray horns of
thoracic & lumbar regions of spinal cord
 Parasympathetic
Division (Craniosacral) cell bodies found in cranial & sacral
regions of the cord
Differ in location of ganglionic
synapse
 Sympathetic
–
–
–
Division -
Paravertebral ganglia - Chain ganglia
Prevertebral ganglia - Collateral ganglia
Postganglionic axon fiber is very long
 Parasympathetic
–
–
–
Division-
Terminal ganglia – close to effectors
Preganglionic axon fiber is long
Postganglionic axon fiber is very short
Neurotransmitters
 Sympathetic
Division - ACh is released at
preganglionic axon terminal; NE or
adrenalin is released at the postganglionic
axon
 Parasympathetic division - ACh is
released at both synapses
* Effect: inhibitory/excitatory depending on
receptors on effectors
Length of influence
 Sympathetic
- is more widespread, more
intense and response is of longer duration
 Parasympathetic - a more controlled
reaction with local effect and shorter
duration
Types of Autonomic Neurons
 Cholinergic
–
All preganglionic neurons & all
parasympathetic postgangionic neurons
 Adrenergic
–
neurons - release ACh
neurons - release NE
Most sympathetic postganglionic neurons
Sympathetic Responses
Pupils and bronchioles dilate
 Heart and respiration rate increases
 Dilation of blood vessels to skeletal muscles
 Constriction of vessels to nonessential organsBLOOD PRESSURE ZOOMS UP
 Secretion and motility to digestive structures
inhibited

Parasympathetic Responses
 Constriction
of pupils and bronchioles
 Decreases respiration rate; slows down the
heart
 Increases blood flow to GI tract
 Decreases blood flow to skeletal muscle
 Kidneys begin to function - urination
 Erection on both male and female