Download ANPS 019 Beneyto-Santonja 12-03

ANPS 019 Beneyto-Santonja 12/03/12
Autonomic Nervous System  Hypothalamus
Somatic Nervous System
 Conscious cortical control of motor activity
 Myelinated innervation of skeletal muscles
 No synapses outside of CNS – innervation by lower motor neurons (LMN)
 Active only when stimulated
 Acetylcholine excitatory input to target
Autonomic Terminology
 Preganglionic neurons – visceral motor neurons located in brainstem and spinal cord,
synapse in autonomic ganglion, use acetylcholine
 Axons of ganglionic neurons are called postganglionic axons
o Cell body in autonomic ganglia
o Innervate visceral effectors:
 Cardiac muscle, smooth muscle, glands, adipose tissues, blood vessels
Autonomic Nervous System
 Involuntary control of visceral function
 Unmyelinated innervation of smooth and cardiac muscle, glands, and internal organs
 One synapce in PNS within ganglion
 Excitatory and inhibitory modulation of intrinsic target activity
 Utilizes multiple neurotransmitters and receptors
How do the somatic and autonomic nervous systems differ?
 Somatic
o Conscious control; one neuron; one neurotransmitter (ACh); Myelinated axon
innervates effector; Innervate skeletal muscle; Only active when stimulated
 Autonomic
o Involuntary; Unmyelinated axon innervated effector; Two neurons; Two
neurotransmitters (ACh & NE); Innervates viscera; Always active, modulate
activity
Sympathetic vs. Parasympathetic Nervous System
 Sympathetic Nervous System
o “Fight or Flight”
 Readies the body for crisis
 Increase in sympathetic activity:
 Stimulates tissue metabolism
 Increases alertness
o Preganglionic neurons are located in thoracic and lumbar spinal cord (T1-L3)
o Preganglionic axons are short since the sympathetic ganglia are located close to
the spinal cord, but are highly branched to innervate many targets
o Postganglionic axons are very long
 Parasympathetic Nervous System
o “Rest and Digest”
 Stimulates visceral activity
 Conserves energy and promotes sedentary activities
o Preganglionic neurons located in brainstem and sacral spinal cord
o Preganglionic axons are long since parasympathetic ganglia are located close to
target organ and branch very little to give finer control
o Postganglionic axons are short
Enteric Nervous System
 Third division of Autonomic NS
 Contains same neurotransmitters as found in the brain
 Allows for complex visceral reflexes to be coordinated locally
Autonomic Integration
 Medulla Oblongata
o Contains nuclei involved in: salvation; swallowing; digestive secretions;
peristalsis (visceral movements); urinary function
o Regulated by hypothalamus
 Hypothalamus
o Interacts with all other portions of brain
o Command center for homeostatic control
o The Hypothalamus regulates all autonomic functions (“the boss”)
 Reticular formation of brain stem  regulation of pupil size, respiration,
heart, blood pressure, swallowing, etc. (Cranial Nerves)
 Spinal Cord  Urination, defecation, erection, and ejaculation reflexes
(Spinal Nerves)
o Maintains homeostatic setpoints
o Part of the Diencephalon – lies below the thalamus
External Structures of the Hypothalamus
 Mamillary bodies:
o Process olfactory and other sensory information
o Control reflexive eating movements: In the movie Awakenings the people who
were ‘frozen’ ate using the reflex centers here and the swallowing centers in the
medulla
 Infundibulum: connects hypothalamus to pituitary gland
The Hypothalamus is made of many small nuclei (neuron clusters)  Each individual nucleus
has a unique function.
The hypothalamus regulates the endocrine system via the pituitary
 Hypothalamus makes releasing factors to stimulate the pituitary gland
 Pituitary gland makes stimulating factors to stimulate glands to make hormones
The hypothalamus regulates circadian (daily) rhythms
 “Biologic Clock” is the suprachiasmatic nucleus
 Regulation of Pineal Gland (melatonin)
The hypothalamus regulates water balance
 Regulates kidney function (retain water)
 Supraoptic nucleus secretes antidiuretic hormone
 Damage to supraoptic nucleus results in diabetes insipidus = pee more + drink more
 “Thirst Center”  Stimulates drinking behavior
The hypothalamus regulates food intake
 “Satiety Center” regulates fullness, suppresses eating behavior
 “Feeding Center” stimulates food consumption
 Responds to peripheral signals
o Leptin from fat cells  inhibit feeding
o Ghrelin from stomach  stimulate feeding
o Insulin from pancreas  inhibit feeding
Genetic contribute to Obesity; Environmental factors contribute as well
The hypothalamus regulates body temperature
 Preoptic area of hypothalamus is the site of the body’s “thermostat”
 Initiates sweating (to reduce body heat)
 Initiates shivering (to increase body heat)
 Thermoregulatory sweating is regulated by hypothalamus
 Emotional sweating is regulated by the limbic system
The hypothalamus controls the ANS
 Hypothalamic neurons send axons down the brainstem and spinal cord to synapse in
areas controlling:
o Cardiovascular function (heart rate, blood pressure)
o Respiration
o Digestion
o Reproduce Activity + Much more
The hypothalamus regulates MANY behaviors via its interaction with the limbic system