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Human Physiology for Exercise Science > Lecture Six > Flashcards

Lecture Six Flashcards

1
Q

What do the main regulatory centres include (nervous system)?

A

-Nervous System
-Somatic Nervous System – voluntary system, skeletal muscle contraction
oAutonomic Nervous System – involuntary system, maintains a state of homeostasis (steady state)
-Sympathetic System = “fight-or-flight”
-Prepares the body for strenuous situations (e.g. physical activity)
-Parasympathetic System = “rest and digest”
-Assists during the quiet phases (e.g. digestion)

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2
Q

What are the similarities between the Nervous & Endocrine system?

A
  • Both systems use the brain and hypothalamus
  • Some molecules are used as both neurotransmitters and hormones
  • Both systems work to regulate bodily functions
  • Some neurons secrete hormones (neurohormones)
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3
Q

What are the differences between the Nervous & Endocrine system?

A

oMode of transport
-Endocrine secretes hormones into the blood stream
-Nervous system secretes neurotransmitters which are directly released onto target cells.
oSpeed of response
-The endocrine system is slower compared to the nervous system
oDuration of response
-Hormones remain in the blood stream for min, days, weeks
-Nervous system is active for as long as the action potentials are sent

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4
Q

What is the role of the Endocrine System?

A
  • Metabolism
  • Control of food intake and digestion
  • Tissue development n Ion levels
  • Water balance
  • Heart rate and blood pressure changes
  • Control of blood glucose and other nutrients
  • Control of reproductive functions
  • Uterine contractions and milk release
  • Immune system function
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5
Q

What are the classes of Chemical Messages and how are they produced/secreted from?

A
  • Autocrine – Secreted from an individual cell and influences the same cell it is secreted from
  • Hormonal Control- Produced by a wide variety of tissues and secreted into extracellular fluid and has a localised effect
  • Neurotransmitter – Produced by neurons and secreted into the synaptic cleft and travels a short distance to influence postsynaptic cells
  • Endocrine – Hormones secreted into the bloodstream, which travel some distance to target tissues
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6
Q

What is Chronic Hormone Secretion?

A
  • A relatively stable concentration is maintained in the blood stream over a long time period
  • e.g. Lipid-soluble hormones
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7
Q

What is Acute Hormone Secretion?

A
  • Hormone concentration alters irregularly and dramatically and changes with each stimulus
  • e.g. Water-soluble hormones
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8
Q

What is Episodic Hormone Secretion?

A
  • Hormones are secreted at regular intervals and concentrations
  • e.g. Lipid-soluble hormones
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9
Q

How are hormones regulated?

A
  1. Neural Activation
  2. Hormone Activation
  3. Hormone Control
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10
Q

What is Neural Activation, what does it cause, what happens if it stops and what do some neurons secrete?

A

-A neuron releases a neurotransmitter that signals the endocrine gland to release a hormone
oA stimulus causes neural action potentials to release neurotransmitters into the synapse of hormone-producing cells which stimulate the release of a hormone.
oIf the stimulus stops then the neural stimulation will stop = hormone release will stop.
oSome neurons secrete chemical messengers into the blood, these hormones are called neurohormones (neuropeptides). These can then cause the secretion of releasing hormones, primarily from the

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11
Q

What is Hormone Activation, what are tropic hormones and what is inhibition?

A

-A hormone (typically called a hormone-releasing factor) will stimulate an endocrine organ/gland to release a different hormone.
oTropic Hormones
-Stimulate the secretion of other hormones from other endocrine glands or organs.
-Inhibition – some hormones prevent the secretion of other hormones

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12
Q

What is Hormone Control, what are hormones sensitive to and what is inhibition?

A
  • Circulating blood-borne molecules stimulate the release of hormones
  • Hormones are sensitive to changes in blood levels of substances.
  • Inhibition – often a hormone with opposing effects is secreted to inhibit the effects of the stimulating hormone.
  • Hormones work together to maintain homeostasis.
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13
Q

What do the main regulatory centres include (endocrine system)?

A

-Endocrine system
oEndocrine glands secrete hormones that travel in the bloodstream to target tissues
oGreek = endo ‘within’ krino ‘to secrete’
oAllows cells to communicate with each other

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14
Q

What does an increased demand for a hormone cause?

A

-Increased demand for a hormone causes appropriate stimuli to induce the endocrine gland to secrete a hormone

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15
Q

When a hormone has done its job what does it need to be?

A
  • Removed from circulation

- The endocrine gland must receive an inhibitory message

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16
Q

How is regulation of a stimulus for homeostatic control done?

A

-Regulation of this stimuli and inhibition in order to maintain homeostatic levels of hormones are done by two major mechanisms;
o Positive Feedback
o Negative Feedback

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17
Q

What is a positive feedback?

A
  • When a hormone:
    1. Stimulates their target cell AND
    2. Promotes the synthesis and secretion of the hormone = further secretion of the hormone.
  • Self-propagating system.
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18
Q

What is a negative feedback?

A

-Most common regulatory mechanism.
-Hormone secretion is inhibited by itself when there
are adequate hormone levels in the blood.
-Self-Limiting system.

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19
Q

What do hormones bind to?

A

-Hormones bind to receptors (proteins) on the target cells.

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20
Q

What do hormones only stimulate and what do they bind to?

A
  • Generally, hormones can only stimulate those cells that have the matching receptor.
  • Some hormones can bind to many (family) receptors which have similar structures.
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21
Q

How do you decrease and increase sensitivity to a hormone?

A
  • Decrease sensitivity to a hormone by ‘down-regulation’ whereby the number of receptors decrease.
  • Increased sensitivity through ‘up-regulation’ results from the increase in the rate of receptor synthesis.
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22
Q

What is the hypothalamus, what does it receive and what is it connected to?

A
  • Is a major control site of the nervous and endocrine systems.
  • It receives information from hormones, emotions and the central nervous system.
  • The hypothalamus is connected to the pituitary gland by an extension = infundibulum.
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23
Q

What what secreted by the hypothalamus and where does it travel to?

A

-Major releasing and inhibiting neurohormones are secreted by the hypothalamus which travel in the portal system to the anterior pituitary gland

24
Q

What is the posterior pituitary gland?

A
  • Also referred to as the Neurohypophysis
  • Extension of the hypothalamus
  • No blood portal system
  • Neuron axons from the hypothalamus travel down the infundibulum and terminate in the posterior pituitary
  • Secrets neurohormones that enter the circulatory system
25
Q

What is the process of stimulating the pituitary gland?

A
  1. Stimuli from the nervous system causes an increase or decrease in action potentials from hypothalamic neurons
  2. Action potentials move through axons down the hypothalamohypophysial tract to the posterior pituitary.
  3. Causes the release of stored neurohormones from the pituitary gland.
  4. Neurohormones circulate in the blood and travel to their target tissues.
26
Q

What is the anti-diuretic hormone secretion dependent?

A

-Secretion is dependent on changes in blood osmolality and volume

27
Q

What is the release of the anti-diuretic stimulation?

A
  • Osmoreceptors respond to changes in blood osmolality
  • Osmolality increases as the concentration of solutes in a solution increase
  • = ↑in action potentials in both osmoreceptors and ADH neurosecretory neurons
  • ↑ADH secretion
28
Q

What is the target tissue and response of the anti-diuretic hormone?

A 
Target Tissue 
-Kidneys 
Response 
-Increased water reabsorption 
n = ↑ in urine output 
n = ↑ blood osmolality 
-Works in reverse if blood osmolality decreases
29
Q

What do baroreceptors respond to and whats the response?

A

-Baroreceptors (situated in the blood vessels) respond to changes in blood pressure
-↓ in blood pressure usually due to a ↓ in blood volume
-↑ in action potentials frequency
= ↑ ADH secretion
= Kidneys retain water

30
Q

After the baroreceptors respond to a stimulus what happens?

A

o Slows any reduction in blood volume
o Also causes vasoconstriction = increase in blood pressure
-Again, this works in reverse if blood pressure is increased
-ADH is influenced by small changes in blood osmolality but quite large changes are required in blood pressure to alter ADH secretion.

31
Q

What is the anterior pituitary gland not made of?

A

-Not made from neural tissue, hormones are not neurohormones

32
Q

Where does the blood supply between the hypothalamus & anterior pituitary occur and where do neurohormones move?

A
  • Blood supply between hypothalamus and anterior pituitary is through a specialised system = hypothalamohypophysial portal system
  • Neurohormones move from a primary capillary network in the hypothalamus down the infundibulum (in hypophysial portal vessels) to the anterior pituitary gland. Hormones are produced in response and carried by a secondary capillary network
33
Q

What do veins carry from the anterior pituitary?

A

-Veins carry hormones from the secondary capillary network to the general circulation

34
Q

What are the secretions of the anterior pituitary gland influenced by and what do trophic hormones stimulate?

A

-The anterior pituitary gland secretions are influenced by releasing and inhibiting hormones from the hypothalamus
-Majority of secretions are Tropic Hormones
o Stimulate the secretion of other hormones from other endocrine glands or organs.

35
Q

What is the growth hormone stimulated by, what is the target cell and response?

A

-Stimulation
o Stressors (low blood glucose) stimulates the release of GH releasing hormone from the hypothalamus
o = ↑ secretion of GH
-Target Tissue
o Most Tissues
-Response
o Stimulates Growth
o Regulates metabolism
o Regulates blood nutrient levels during fasting and post meal
-Regulated by negative feedback and GH inhibiting hormone decreases the secretion of GH

36
Q

What is the thyroid-stimulating hormone stimulated by, whats the target tissue and response?

A

-Thyrotropin
-Stimulation
o Controlled by the secretion of Thyroid releasing hormone (TRH) and thyroid hormone
-Target Tissue
o Thyroid Gland
-Response
o Stimulates the synthesis and secretion of thyroid hormones
-Inhibited by thyroid hormones
-Secreted in an episodic manner

37
Q

What is the adrenocorticotrophic hormone stimulated by, whats the target tissue and the response?

A

-Stimulation
o Released in response to Corticotropin- releasing hormone (CRH)
-Target Tissue
o Adrenal Cortex
-Response
o Increased secretion of glucocorticoid hormones

38
Q

What does the thyroid gland secrete?

A

o Thyroid hormones (90%)
-T3 – Triiodothyronine (10%)
-T4 – Thyroxine (80%)
o Calcitonin (10%)

39
Q

What is the thyroid gland made of and whats between them?

A

-Thyroid gland is made of many follicles
o Colloid (gelatinous fluid) fills the follicles
o Colloid is composed of thyroglobin which stores thyroid hormones
-Between the follicles are parafollicular cells
o These cells secrete Calcitonin

40
Q

What is the thyroid hormone stimulated by, whats the target tissue and the response?

A

-Stimulation
o Thyroid Releasing Hormone (TRH) and Thyroid Stimulating Hormone (TSH)
-Target Tissues
o Most cells in the body
-Response
o Regulates metabolism, alters the metabolic rate
o Affects body temperature as a result of influencing mechanisms that create heat production e.g. metabolism, mitochondria activity
o Growth and maturation of organs (bone, hair, nervous tissue, connective tissue)
-Decreased levels of TSH decrease thyroid hormone release
-Thyroid hormones in the blood provide negative feedback which cause a decrease in secretion

41
Q

What is the stimulation of the secretion of calcitonin, whats the target tissue and the response?

A 
-Stimulation 
o	Secreted in response to high blood calcium (Ca2+) levels 
-Target Tissue 
o	Bone 
-Response 
o	Decreases osteoclast activity 
-Osteoclast cells = bone reabsorption 
o	Lengthens the life of osteoblast 
-Osteoblast cells = assists bone formation 
o	= ↓ in Ca2+ (and phosphate) levels
42
Q

What are the symptoms of hyper-secretion of the thyroid gland?

A
  • Increased metabolic rate
  • Increased heat production = elevated body temperature
  • Weight loss
  • Increased appetite
  • Rapid heart rate
  • Enlarged thyroid gland (Goiter)
43
Q

What are the symptoms of hypo-secretion of the thyroid gland?

A
  • Decreased rate of metabolism
  • Low body temperature
  • Weight gain
  • Decreased appetite
  • Reduced heart rate
  • Abnormal growth, maturation and nervous system development
44
Q

Describe where the parathyroid hormone is and what are the types of cells on it?

A

-Embedded in the posterior part of the Thyroid gland
-2 each side
-2 types of cells
o Chief Cells
-Secretes Parathyroid Hormone (PTH)
o Oxyphils Cells
-Function unknown

45
Q

What does the parathyroid hormone assist with, what is it stimulated by, what is the target tissue and the response?

A

-Parathyroid Hormone
o Assists with the regulation of Ca2+ levels
n Stimulation
o A decrease in blood Ca2+ levels
n Target Tissue
o Bone, kidneys, small intestine
n Response
o Binds to osteoblast receptors which
-Increases Osteoclast activity and number
= bone reabsorption = release of Ca2+ (and phosphate)
= ↑ in blood Ca2+ levels
o Stimulates Ca2+ uptake within the kidneys
= less Ca2+ in the urine
= ↑ in blood Ca2+ levels
o Increased absorption in the small intestine of Ca2+ (and phosphate)
= ↑ in blood Ca2+ levels
-Inhibited by increased Ca2+ levels

46
Q

Where are the adrenal gland situated, what are they comprised of and what is the adrenal cortex comprised of?

A

-Situated on the superior portion of the kidneys
-Adrenal Glands are comprised of an;
o Inner Medulla
o Outer Cortex
-Adrenal Cortex is comprised of small cells in 3 layers
o Zona Glomerulosa
o Zona Fasciculata
o Zona Reticularis

47
Q

What is the adrenal medulla hormone stimulated by and whats the target tissue?

A

-Catecholamines - Epinephrine (80%) and Norepinephrine (20%)
-Neurohormones
-Stimulation
o Numerous stimuli exist;
o Emotional excitement
o Injury
o Exercise
o Stress
o Low blood glucose
-Target Tissue
o Heart, liver, blood vessels and adipose tissue

48
Q

What is mineralocorticoids stimulated by, whats the target tissue and whats the response?

A

-Zona Glomerulosa cells secrete Mineralocorticoids
o Mainly the hormone Aldosterone
-Stimulation
o Low blood pressure
-Target Tissue
o Kidney
-Response
o Increases Sodium (Na+) reabsorption = ↑ blood Na+
-Causes ↑ water reabsorption = ñ blood volume
o ↑ excretion of potassium (K+) and hydrogen ions (H+)

49
Q

What is cortisol stimulated by, whats the target tissue and the response?

A

-Stimulation
o Low blood glucose and stress stimulate CRH
o CRH stimulates ACTH which travels to the adrenal cortex = ↑ Cortisol secretion
-Target Tissue
o Most Tissues – skeletal muscle, liver, adipose tissue, immune tissues
-Response
o Metabolic
-↑ protein and lipid breakdown
-↑ blood glucose levels
o Developmental
-Maturation of tissues
o Anti-inflammatory
-Decrease the intensity of the inflammatory and immune response
-↓ number of inflammatory chemicals and white blood cells
-Negative feedback of ACTH and Cortisol inhibits CRH secretion
-High levels of Cortisol inhibit ACTH

50
Q

What do zona fasciculata cells secrete?

A

Glucocorticoid Hormones

51
Q

What cells secrete Androgens, what are they and whats their function?

A
  • Zona Reticularis cells secrete Androgens
  • Steroid hormones
  • Function as weak androgens
  • Most androgens are secreted by reproductive system
  • Some adrenal androgens are secreted and converted in peripheral tissues to testosterone.
52
Q

What are the target tissues of testosterone & oestrogen and whats the response?

A

-Target Tissues
o Many tissues
-Response
o Androgen causes the development of male secondary sex characteristics (not as potent compared to testosterone secreted from the testes)
o Development of secondary sex characteristics in females

53
Q

Where does the pancreas lie, what does it do as an exocrine and endocrine gland?

A

-Lies under the peritoneum and between the stomach and duodenum
-Both an endocrine and exocrine gland.
o Exocrine Gland
-Secretions are secreted via a duct external to the gland either onto a bodily surface or inside the body.
-Acini cells produce pancreatic juice which is carried to the small intestine (more on this in Digestive Lecture).
o Endocrine Gland
-Islets of Langerhans make up the endocrine portion
-Alpha cells (20%) secrete glucagon
-Beta cells (75%) secrete insulin

54
Q

What stimulates insulin secretion, whats the target tissue and the response?

A

-Stimulation
o High blood glucose levels
o Parasympathetic stimulation – no need for available glucose
-Target Tissue
o Liver, skeletal muscle, adipose tissue and satiety centre of the brain
-Response
o ↑ the uptake of glucose and amino acids

55
Q

What stimulates glucagon secretion, whats the target tissue and the response?

A

-Stimulation
o Low blood glucose levels
o Sympathetic stimulation – preparation for exercise where we need available glucose
-Target Tissue
o Mainly Liver – as most glucagon is delivered directly to the liver
-Response
o Increases blood glucose levels, primarily released from the liver and occurs very rapidly
-Inhibited by high blood glucose levels

Human Physiology for Exercise Science (14 decks)

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