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Physiology 2130 > Neuroscience > Flashcards

Neuroscience Flashcards

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
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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

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3
Q

Major Function of the

SUPRAOPTIC NUCLEUS

A

Water balance

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4
Q

Major Function of the

SUPRAOCHIASMATIC NUCLEUS

A

Biological Clock

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5
Q

Major Function of the

VENTROMEDIAL NUCLEUS

A

Satiety

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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
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7
Q

Major Function of the

LATERAL NUCLEUS

A

Feeding centre

  • works with the paraventricular nucleus
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8
Q

Major Function of the

PREOPTIC/ANTERIOR HYPOTHALAMIC REGION

A

Blood pressure, Body temperature
(Vasodilation = PNS)

  • 2 nuclei
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9
Q

Major Function of the

POSTERIOR HYPOTHALAMUS

A

Blood pressure, Body temperature

Vasoconstriction = SNS

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10
Q

Major Function of the

BASOMEDIAL HYPOTHALAMUS

A

Anterior/Posterior Pituitary Releasing Factors

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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)
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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
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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)

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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)

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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.

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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

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17
Q

3 main stimuli known to elicit thirst and the release of vasopressin (ADH)?

A
  1. low ECF
  2. low Osmolarity
  3. low Arterial blood pressure
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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)
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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
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20
Q

Define “obesity”

A

Having abnormal/excessive fat accumulation that presents a risk to an individual’s health

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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
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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

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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”

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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
Q

What are physiological signals that contribute to food intake?

A

= 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
Q

What is Leptin?

A

= 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
Q

What’s the function of Orexin?

A
  • when it’s present, it causes an INCREASE in appetite
  • housed in Lateral Hypothalamic Nucleus
  • orexin release is inhibited by excess leptin
28
Q

What’s the function of NPY?

A
  • it’s release is inhibited with high leptin levels

- causes an increase in food intake

29
Q

What’s the function of POMC?

A
  • Activated with high leptin levels –> releases alpha-MSH

- causes increased energy expenditure and inhibits food intake

30
Q

What’s the function of the paraventricular nucleus in regards to food intake?

A
  • part of the feeding centre

- directly increases hunger by increasing energy expenditure once alpha-MSH binds to its MC4-R

31
Q

What’s the function of the dorsomedial hypothalamus in regards to food intake?

A
  • responds to NPY
  • Low leptin levels cause activation of this pathway –> NPY binds to NPY-R –> stimulates dorsomedial hypothalamus –> increases food intake
32
Q

What’s the function of the lateral hypothalamus in regards to food intake?

A
  • part of the feeding centre

- releases orexin in response to low leptin

33
Q

What is Metabolic Syndrome?

A

= 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
Q

What are the end points when a person starts this metabolic syndrome disease process?

A

Diabetes, hyperlipidemia, hypertension
–> Atherosclerosis

High risk of stroke and cardiac arrest

35
Q

What % of global health care used towards alleviation of metabolic syndrome?

A

75%

36
Q

What is Anorexia Nervosa?

A

= psychological disorder where you see yourself as heavier than you really are

  • BMI
37
Q

What is Bulimia Nervosa?

A

= psychological disorder involving binge eating and then throwing it up (purging) to maintain a certain image

  • involves both frontal cortex and limbic system
38
Q

What are Circadian Rhythms?

A

= 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
Q

Examples of circadian rhythms

A
  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
Q

Define Thermoregulation

A

= homeostatic regulation of normal body temp within narrow limits

Heat Input + Heat Production = Heat Loss

41
Q

What are the 4 ways that heat can be produced? Which is the most effective?

A
  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
Q

What are the main heat loss mechanisms? What’s the % breakdown?

A
  1. Convection (35%)
  2. Radiation (34%)
  3. Evaporation (27%)
  4. Conduction (1%)
43
Q

What is RADIATION?

A

= transfer of heat energy as EM waves

44
Q

What is CONDUCTION?

A

= 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
Q

What is CONVECTION?

A

= 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
Q

What is EVAPORATION?

A

= 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
Q

What are thermoreceptors?

A

= sensory receptors that detect absolute and relative changes in temperature

  • unmyelinated nerve endings
  • detect relative changes in hot or cold within a range
48
Q

What are the two types of thermoreceptors? Where are they located?

A
  1. Warm Receptors –> Dermis

2. Cold Receptors –> Dermis (located deeper within)

49
Q

Internal environment factors/actions and external environment factors/actions that interact in the
Physiological Response to the Cold

A
  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
Q

What the “hypothalamic set point mechanism”? What is the set-point temperature?

A

= a genetically determined value that is present from brith

37˚C

51
Q

What is the effect of stimulation of the POSTERIOR hypothalamus on Temperature regulation?

A

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
Q

What is the effect of stimulation of the ANTERIOR hypothalamus on Temperature regulation?

A
  • stimulates posterior hypothalamus heat loss mechanism
  • detect increases in temp. which get relayed to posterior hypothalamus –> blood perfuses (permeates) the anterior hypothalamus)
53
Q

Different ways to measure body temp. and their effectiveness

A
  1. Rectal = most effective
  2. Tongue = 2nd most effective
  3. Armpits = least effective
54
Q

What is Fever?

A

= 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
Q

What is Heat Exhaustion?

A

= 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
Q

What is Heat Stroke?

A

= 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
Q

Symptoms of Heat Stroke

A
  • 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
Q

Possible Treatments for Heat Stroke

A
  • stay somewhere cool
  • apply cold compress to neck, armpits, groin
  • give fluids
  • elevate feet
  • have person lie down

Physiology 2130 (3 decks)

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