1
Q
Define “Hypothalamus”
A
= Small structure at the base of the brain, made up of many different nuclei which control diff. bodily functions (they all talk to each other)
- integration of autonomic, endocrine, behavioural responses for homeostatic regulation of internal environment for adaptation to continuously changing external environment
- master controller of ANS
- beneath the thalamus, connected to pituitary gland (just above the pituitary) –> Posterior pituitary is part of the hypothalamus!!
- extends from near the optic chasm to the mammillary bodies
2
Q
Functions of the hypothalamus
A
1) Control of ANS
2) Neuroendocrine control
3) Reproductive
4) H2O Balance/exchange
5) Sodium balance/exchange
6) Body energy balance/exchange
7) Drive and emotions
8) Circadian rhythms
9) Body temperature regulation
3
Q
Major Function of the
SUPRAOPTIC NUCLEUS
A
Water balance
4
Q
Major Function of the
SUPRAOCHIASMATIC NUCLEUS
A
Biological Clock
5
Q
Major Function of the
VENTROMEDIAL NUCLEUS
A
Satiety
6
Q
Major Function of the
PARAVENTRICULAR NUCLEUS
A
Water balance, stress, feeding
- works with lateral for feeding functions, but takes a bit more time
7
Q
Major Function of the
LATERAL NUCLEUS
A
Feeding centre
- works with the paraventricular nucleus
8
Q
Major Function of the
PREOPTIC/ANTERIOR HYPOTHALAMIC REGION
A
Blood pressure, Body temperature
(Vasodilation = PNS)
- 2 nuclei
9
Q
Major Function of the
POSTERIOR HYPOTHALAMUS
A
Blood pressure, Body temperature
Vasoconstriction = SNS
10
Q
Major Function of the
BASOMEDIAL HYPOTHALAMUS
A
Anterior/Posterior Pituitary Releasing Factors
11
Q
Effect of stimulation of the Posterior Hypothalamus?
A
–> Sympathetic (fight or flight)
- INCREASES Blood Pressure
- INCREASES Heart Rate
- DECREASES Gastrointestinal motility
- DILATES Pupils (therefore, see more)
12
Q
Effect of stimulation of the Anterior Hypothalamus?
A
–> Parasympathetic (rest and digest)
- DECREASES blood pressure
- DECREASES heart rate
- INCREASES gastric motility
- CONSTRICTS pupils
13
Q
How do the supraoptic and paraventricular nuclei interface with the pituitary gland?
A
Through the axon terminals of both nuclei (this is how hormones are transported)
14
Q
What hormones are produced in the hypothalamus and released directly into circulation? Which nuclei produces the hormones?
A
Oxytocin (paraventricular nuclei)
ADH (supraoptic nuclei)
15
Q
The _______ hypothalamus secretes _________, which reach the __________ ________ gland via the _____________.
A
The basomedial hypothalamus secretes releasing hormones, which reach the anterior pituitary gland via the hypophyseal portal system.
16
Q
What is a neural-humoral reflex?
An example?
A
Neural input/stimulus –> activates neural system –> hormone release in system
i.e. oxytocin = positive feedback system
17
Q
3 main stimuli known to elicit thirst and the release of vasopressin (ADH)?
A
- low ECF
- low Osmolarity
- low Arterial blood pressure
18
Q
How is water loss regulated?
A
- multiple initial stimuli stimulate the decrease in ECF and decreased arterial BP –> causes a change in the left atrial stretch receptors
- this signal sent to hypothalamus, stimulates hypothalamic neutrons
- vasopressin release from pituitary (anterior –> pituitary)
- causes arteriolar vasoconstriction (relieves arterial BP)
- increases H2O permeability in distal/collecting tubes
which increases H2O reabsorption and decreased
urine output –> increase plasma vol. (relieves low ECF)
19
Q
How is water intake controlled?
A
- INCREASED osmolarity
- stimulates hypothalamic osmoreceptors
- this stimulates hypothalamic neutrons
- increases thirst
- drink water –> DECREASES (relieves) plasma osmolarity
20
Q
Define “obesity”
A
Having abnormal/excessive fat accumulation that presents a risk to an individual’s health
21
Q
What is BMI?
A
Body Mass Index = Mass/(Height^2) = kg/metres^2
- obese = BMI ≥ 30
- tells us how at risk we are for developing certain diseases/illnesses
- problem = doesn’t take into account muscle mass (therefore, it’s a crude measurement)
- now we look at waist:hip ratio instead
22
Q
Why do we eat and over-eat?
A
Genetic Changes + Lifestyle Factors + Physiological Signals
We overeat due to lifestyle factors and social habits
we override physiological signals
23
Q
What are lifestyle factors that contribute to food intake?
A
- taste and smell permeability
- availability
- clock
- cues and social habits
Your “COGNITIVE AND EMOTIONAL BRAIN”
24
Q
What are genetic changes that contribute to food intake?
A
= changes in genes that make you want to eat (can’t control!!)
- epigenetic = gene expression changed
- imprinting
Your “COGNITIVE AND EMOTIONAL BRAIN”
25
What are physiological signals that contribute to food intake?
= parts in your body that provide signals telling you to eat/not eat; often overrided
Energy Balance = Energy Intake - Energy Expenditure (aim for this to be 0)
Your "METABOLIC BRAIN"
26
What is Leptin?
= hormone produced by fat cells (adipose tissue) = a satiety signal
- main physiological signal for food intake
- lot of fat = produce a lot of leptin = signals hypothalamus, resulting in ... decreased food intake, increased expenditure, increased blood pressure
- high levels activate arcuate nucleus, a satiety centre
- low levels activate lateral + paraventricular nuclei, feeding centre
27
What's the function of Orexin?
- when it's present, it causes an INCREASE in appetite
- housed in Lateral Hypothalamic Nucleus
- orexin release is inhibited by excess leptin
28
What's the function of NPY?
- it's release is inhibited with high leptin levels
| - causes an increase in food intake
29
What's the function of POMC?
- Activated with high leptin levels --> releases alpha-MSH
| - causes increased energy expenditure and inhibits food intake
30
What's the function of the paraventricular nucleus in regards to food intake?
- part of the feeding centre
| - directly increases hunger by increasing energy expenditure once alpha-MSH binds to its MC4-R
31
What's the function of the dorsomedial hypothalamus in regards to food intake?
- responds to NPY
- Low leptin levels cause activation of this pathway --> NPY binds to NPY-R --> stimulates dorsomedial hypothalamus --> increases food intake
32
What's the function of the lateral hypothalamus in regards to food intake?
- part of the feeding centre
| - releases orexin in response to low leptin
33
What is Metabolic Syndrome?
= group of conditions that puts you at higher risk for developing type 2 diabetes, heart diseases, other heart problems
If you have 3 OR MORE of...
- high fasting blood glucose levels
- high blood pressure
- high level of triglycerides
- low levels of HDL
- abdominal obesity (too much fat around your waist)
- -> the more of the conditions you have = higher risk of developing the diseases
- -> unsure what causes metabolic syndrome (maybe related to insulin resistance? Genetic, old age, lifestyle also plays a role)
34
What are the end points when a person starts this metabolic syndrome disease process?
Diabetes, hyperlipidemia, hypertension
--> Atherosclerosis
High risk of stroke and cardiac arrest
35
What % of global health care used towards alleviation of metabolic syndrome?
75%
36
What is Anorexia Nervosa?
= psychological disorder where you see yourself as heavier than you really are
- BMI
37
What is Bulimia Nervosa?
= psychological disorder involving binge eating and then throwing it up (purging) to maintain a certain image
- involves both frontal cortex and limbic system
38
What are Circadian Rhythms?
= natural pattern of physiological/behavioural processes that are timed to a near 24hr period
- drive by natural dark-light cycles, but will persist under constant environmental conditions
- controlled by SUPRACHIASMATIC Nucleus (biological clock) --> controls melatonin release
- LED lights alter cycle by tricking the system, it suppresses melatonin levels leading to decreased ability to fall asleep
39
Examples of circadian rhythms
1. Sleep
2. Food/H2O Intake
3. Urine production
- most at bed, also when you wake up
4. Blood pressure
- highest in the AM, rises until noon, decreases @ 6-7pm
5. Platelet aggregation
- platelets come together at night
6. White blood cell production
7. Body temperature changes
- during the day
8. Hormone release
- corticosterone (cortisol), LH, melatonin
9. Menstrual cycle
- longer cycle
40
Define Thermoregulation
= homeostatic regulation of normal body temp within narrow limits
Heat Input + Heat Production = Heat Loss
41
What are the 4 ways that heat can be produced? Which is the most effective?
1. METABOLIC ACTIVITY = heat byproduct from any biochemical reaction
2. NON-SHIVERING THERMOGENESIS = hormonal release (T3/T4) that causes an increase in heat production, without muscle contractions
3. MUSCLE ACTIVITY = generates heat when you work out
4. SHIVERING = involuntary rhythmic muscle contractions
- --> most efficient way!!
42
What are the main heat loss mechanisms? What's the % breakdown?
1. Convection (35%)
2. Radiation (34%)
3. Evaporation (27%)
4. Conduction (1%)
43
What is RADIATION?
= transfer of heat energy as EM waves
44
What is CONDUCTION?
= transfer from warmer to cooler object through direction contact
- heat transferred through movement of thermal energy from molecule to adjacent molecule
- not very effective
45
What is CONVECTION?
= transfer of heat energy by air currents
- used to cool ourselves down, transfer of warmth to the air molecules around you
- cool arm warmed by body via conduction rises, and is replaced by more cool air
46
What is EVAPORATION?
= conversion of liquid (sweat) into gaseous vapour
- helps cool us down
- brings fluid to surface of body via sweat glands (active process)
- process requires heat, which is absorbed from the skin
47
What are thermoreceptors?
= sensory receptors that detect absolute and relative changes in temperature
- unmyelinated nerve endings
- detect relative changes in hot or cold within a range
48
What are the two types of thermoreceptors? Where are they located?
1. Warm Receptors --> Dermis
| 2. Cold Receptors --> Dermis (located deeper within)
49
Internal environment factors/actions and external environment factors/actions that interact in the
Physiological Response to the Cold
1. REGULATION OF ENDOCRINE SECRETION
- Hypothalamus detects fall in the temperature
- releases TSH-RH (thyroid stimulating hormone releasing hormone)
- TSH-RH acts at the anterior pituitary to increase TSH secretion
- TSH stimulates thyroid to release thyroxine (hormone)
- thyroxine acts act cells to increase basal metabolic rate --> increases heat production + temperature
2. REGULATION OF ANS ACTIVITY
- Hypothalamus detects fall in temp., stimulates SNS
- leads to constriction of blood vessels in skin --> less blood will flow to skin --> reduces heat loss
- increased SNS activity stimulates shivering (piloerection in animals) --> increases heat production/reduces heat loss
3. REGULATION OF EMOTIONS/MOTIVATED BEHAVIOUR
- cold is a stimulus for goal directed, motivated behaviours (seeking shelter, turning up thermostat, putting on sweater)
- lead to reduced heat loss
50
What the "hypothalamic set point mechanism"? What is the set-point temperature?
= a genetically determined value that is present from brith
37˚C
51
What is the effect of stimulation of the POSTERIOR hypothalamus on Temperature regulation?
Posterior = heat promoting/heat-loss centre
- responsible for activating sweat glands and dilating blood vessels when hot
- activating skeletal muscles and constricting blood vessels when cool
52
What is the effect of stimulation of the ANTERIOR hypothalamus on Temperature regulation?
- stimulates posterior hypothalamus heat loss mechanism
- detect increases in temp. which get relayed to posterior hypothalamus --> blood perfuses (permeates) the anterior hypothalamus)
53
Different ways to measure body temp. and their effectiveness
1. Rectal = most effective
2. Tongue = 2nd most effective
3. Armpits = least effective
54
What is Fever?
= body's response to a foreign object
- increased body temp. will denature proteins
- Interleukin-1 (byproduct of phagocytic cells/lymphokines) goes to hypothalamus, raises body's set point to accommodate this protein destruction
- babies are great thermoregulatory (due to high SA: volume ratio)
55
What is Heat Exhaustion?
= when we thermoregulate so well that we end up losing too much water so the blood volume decreases, BP decreases, enter circulatory shock (decreased MAP and decreased CO)
- can cause heat stroke if not treated quickly
Heat --> cutaneous arteriolar dilation and excessive sweating ---> Hypovolemia --> circulatory shock
56
What is Heat Stroke?
= severe elevation in core temp. and the inability to bring it back to set point (poor thermoregulation)
- high temps. impair CNS and damage organs and tissues
57
Symptoms of Heat Stroke
- extremely hot body temp.
- red, hot, dry skin
- rapid, strong pulse
- headache
- dizziness/nausea
- confusion/unconsciousness
- body isn't regulated (therefore, don't sweat)
58
Possible Treatments for Heat Stroke
- stay somewhere cool
- apply cold compress to neck, armpits, groin
- give fluids
- elevate feet
- have person lie down
Physiology 2130
flashcards
Decks in class (3)
# Cards
