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Chapter 1 Organization of the Nervous System
Hypothalamus
Outline
• Function of the Hypothalamus
• Regulation of Body Temperature
• Autonomic Nervous System
I. Function of the Hypothalamus
• Reference– Adina Michael-Titus, et al. System of the Body – The
Nervous System. 2nd version, Elsevier Limited, 2011. P19 – 20
– 姚泰主编, 8年制及 1年制临床医学等专用生理学,第二版,人民卫生出版社, 2010年。 P 483 – 485。
Tu :19.17
Hypothalamus
Hypothalamic Functions
• Food Intake• Water Balance• Sleep/wake cycle• Emotions and behavior• Circadian• Endocrine Functions• Body Temperature• Autonomic Nervous System
Food Intake
• Ventromedial and Paraventricular Nuclei are satiety centers– Lesion causes obesity– Through disrupting satiety input to the periventricular nucleus
• Lateral HT is feeding center – Stimulation cause food and water intake– Lesion causes starvation behavior– Through damage the medial forebrain bundle, leading to neglect syndrome – no
motivation to eat
Water Balance
• Thirst center in the hypothalamus (supraotic nucleus) is stimulated by:– Cellular dehydration– Decreased salivary production– Increased blood osmotic pressure– Decreased blood volume
• Thirst center response– Release vasopressin– Cause sensation of thirst
Sleep/Wake Cycle:
suprachiasmatic nuc is biological clock
preoptic nuc can initiate sleep
lat HT can change cortical arousal
post HT lesion can cause coma or impaired arousal
Emotions and Behavior
Ventromedial lesions can cause viciousness/rage
Posterior HT stimulates sympathetic functions
Anterior HT stimulates parasympathetic functions
Mamillary nuclei recent memory
Almost all land animals coordinate their
behavior according to circadian rhythms
Suprachiasmatic Nuclei (SCN)
Circadian
Circadian Rhythms of Physiological Functions
Endocrine Function
• Regulation of Adenohypophysis
• Secretion of Hormones (Vasopressin and Oxytocin)
Functions of the Hypothalamus
• Food intake
• Water balance
• Sleep/wake cycle
• Emotions and behavior
• Circadian
• Endocrine Function
• Body temperature
• Autonomic Nervous System
II Energy metabolism and body temperature
Reference
• Arthur C. Guyton, John E. Hall. Textbook of Medical Physiology, 11th edition, Elsevier Science, 2006. P 881-900
• 姚泰主编, 8年制及 7年制临床医学等专用生理学,第二版,人民卫生出版社, 2010年。 P 483 – 485。
Section 1 Energy Metabolism
materialsynthesis
materialbreakdown
releaseenergy
requireenergy
materialmetabolism
energy metabolism
Metabolism
Anabolism Catabolism
Energy storage, liberation, transfer and utilization
Energy balance
Energy input = energy output
heatFood heat heat ATP cellular functions heat
metabolismFood heat
Metabolic Rate
• The amount of energy liberated from a living organism per unit of time
• Expressed in terms of the rate of heat liberation during the chemical reactions
Measurement of the metabolic rate
• Direct calorimetry• Indirect calorimetry
– Caloric value / thermal equivalent of food– Oxygen consumption / thermal equivalent of
oxygen ( 1 L)– Respiratory quotient ( CO2 / O2)
Factors that affect the metabolic rate
• Exercise - increase in metabolic rate• Ingestion of food - Increase metabolic rate
– The specific dynamic action of protein
• Emotional state• Environmental temperature
– 20-30 °C have stable metabolic rate– < 20 or >30°C , metabolic rate is increased
• Other factors (sleep, sex, age, etc.)
Component of Energy Expenditure
Basal metabolic rate (BMR)
• minimum level of energy required to exist– a person is at basal condition (complete rest)
• useful for diagnosing the diseases:– Hyperthyroidism, hypothyroidism
Basal conditions
• Fasted for at least 12 hours• After a night of restful sleep• No strenuous activity is performed for at least 1
hour before the test• All psychic and physical factors that cause
excitement must be eliminated• The temperature 25 – 30 °C • No physical activity is permitted during the test
Section 2 Body temperature
Skin and Core Temperature
• Skin temperature– the temperature of the skin and tissues immediately underlying
the skin. rises and falls with the temperature of the surroundings
• Core temperature – the temperature of the deep tissues of the body – the “core” of
the body. – remains almost constant, varying not more than 1 °C
• Rectal T: 36.9-37.9 °C • Oral T: 36.7-37.7 °C • Axillary T: 36.0-37.4 °C
Range of Body TemperatureRange of Body Temperature
Factors affecting normal temperature
• Circadian rhythm– In the early morning, the body T is the lowest.
– In late afternoon or early evening, it is the highest.
• Age– Newborn child > adult > old person
• Sex– Women > man 0.3 °C
• Muscular activity• Other factors: emotion, eating, change in climate
Heat Production
• BMR of all the cells• Extra metabolism caused by
– muscle activity
– hormone (thyroxine, growth hormone and testosterone)
– the effect of epinephrine,
– norepinephrine and sympathetic stimulation on the cells
– increased chemical activity in the cells themselves
Heat Loss
• The major organ to loss heat is the skin• Blood flow to the skin from the body core provides heat transfer
Methods of heat loss from the skin to the surroundings
Effect of Environment air Temperatureon Conductance of Heat from the Body
•1) Insensible perspiration
•2) Sweating•Innervated mainly by
sympathetic cholinergic nerve
(acetylcholine)
•Caused by nervous reflex
•Mechanism of sweat secretion
• Primary secretion• • reabsorption
• Sweat (urea, lactic acid, K+ )
Evaporation
Regulation of the body temperature
• Behavioral control of the body temperature
• Autonomic control of the body temperature
Feedback mechanisms of regulation of the body temperature
• Temperature receptor– Peripheral temperature receptor
• Locations: skin, mucous,, abdominal viscera• Types: cold receptor and warmth receptor• cold receptor > warmth receptor
– Central temperature receptor• Locations: spinal cord, preoptic and anterior hypothalamic area of the
hypothalamus (PO/AH)• Types: heat-sensitive neurons and cold-sensitive neurons
• Temperature-regulating center– 1) The thermoregulating center is mainly in the hypothalamus– 2) The PO/AH area is the basic thermostatic temperature
controlling center
Feedback mechanisms of regulation of the body temperature
• Efferent pathways: Control of the heat loss and heat production
– Control of the skin vascular tone and sweating by sympathetic nerve system
– Changes of the muscular tension by somatic motor nerve system
– Control of the metabolic rate by altering the function of endocrine system, mainly the hormone secretion of the thyroid glands or adrenal medulla
“Set-point”
37 °C
PO/AH area
T > 37 °C
Production < loss
T < 37 °C
Production > loss
Fever
III Autonomic Nervous System
• Reference– Adina Michael-Titus, et al. System of the Body – The
Nervous System. 2nd version, Elsevier Limited, 2011. P24 – 28
– 姚泰主编, 8年制及 7年制临床医学等专用生理学,第二版,人民卫生出版社, 2010年。 P 478 – 482
Section 1. Basic of the ANS
• Including – parasympathetic– sympathetic– enteric divisions
• Coordinates cardiovascular, respiratory, digestive, excretory and reproductive systems
• The enteric system– an independent nervous system responsible for
regulation of digestive functions.
Somatic and Autonomic Nervous System
Somatic and Autonomic Nervous System
Somatic• Skeletal muscle• Conscious and
unconscious movement• Skeletal muscle
contracts• One synapse• Acetylcholine
Autonomic• Smooth and cardiac
muscle and glands• Unconscious regulation• Target tissues
stimulated or inhibited• Two synapses• Acetycholine by
preganglionic neurons and ACh or norepinephrine by postganglionic neurons
• Preganglionic cell bodies in lateral horns of spinal cord T1-L2
Sympathetic Division
Parasympathetic Division
• Preganglionic cell bodies in nuclei of brainstem or lateral parts of spinal cord gray matter from S2-S4– Preganglionic axons from
brain pass to ganglia through cranial nerves
– Preganglionic axons from sacral region pass through pelvic nerves to ganglia
Preganglionic axons pass to terminal ganglia within wall of or near organ innervated
Parasympathetic and sympathetic
nerve distribution
2. Neurotransmitters and Neuroreceptors
• Acetylcholine and Norepinephrine
• All preganglionic neurons are cholinergic
• Parasympathetic post ganglionic neurons are cholinergic
• Sympathetic post ganglionic neurons are adrenergic except
• Sympathetics innervating sweat glands, blood vessels in skeletal muscle, and piloerection muscles are cholinergic
Neurotransmitters
ACh AChSweatglands
Striatedmuscle
AChSOMATIC NERVOUS SYSTEM
HeartSm. mus.Glands
ACh AChParasympathetic
AChE, NE
Ad. M.
HeartSm. mus.Glands
ACh NE
AUTONOMIC NERVOUS SYSTEM
Sympathetic
Section 3 Function of the Sympathetic and Parasympathetic Nerve
SNS
• Sympathetic nervous system prototypically “fight” or “flight”.
• Associated with increased
energy expenditure
cardiopulmonary adjustments for intense activity,
blood flow adjustments for maximum energy expenditure.
SNS - Fight & Flight Reaction
You’re walking alone at night and all the sudden you hear an unfamiliar noise near by… In a matter of seconds,
your heart rate increases dramatically, blood vessels in your skeletal muscles dilate, blood vessels in the visceral muscles constrict, digestion is ceased, your liver ramps up glucose release, your pupils dilate, salivary production decreases, sweat increases.
Parasympathetic Nervous System
• If that noise turns out to be the result of wind, then the body is returned to “pre-noise” state.
• This is the job of the parasympathetic nervous system.
Autonomic Nervous System• Parasympathicus• Wind down,
relaxation, digestion• Dominated by
Acetylcholine
• Sympathicus • Fight & Flight
Reaction• Dominated by
Noradrenaline (Adrenaline)
• Fear, exercise, rage
Interactions of the ANS
• Most visceral organs are innervated by both types of nerves.
• Most blood vessels are innervated only by sympathetic nerves.
• PS activity dominates the heart and GI tract.• Activation of the sympathetic division causes wide spread,
long-lasting mobilization of the fight-or-flight response. • PS effects are highly localized and short lived.
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