Lecture Objectives for: Neural and Hormonal Thermoregulation

Question 1

What’s Homeothermy?

Answer 1

Body tempterature is kept constant

Question 2

What’s Poikilothermy?

Answer 2

Body temperature varies

Question 3

What’s Heterothermy?

Answer 3

Body temperature is maintained at different values

Question 4

What’s Endothermy?

Answer 4

Body temperature is controlled by internal metabolism

Question 5

What’s Ectothermy?

Answer 5

Body temperature is controlled by environmental sources

Question 6

What happens when organophosphate binds acetylcholinesterase?

Answer 6

This causes ACh continues binding to muscarinic and nicotinic receptor overstimulation. (first, spastic paralysis then flaccid paralysis - the nicotinic receptor desensitizes)

Question 7

What are the location of the body’s thermoreceptors?

Answer 7

In the skin (the periphery) and in the hypothalamus, digestive tract, and blood vessels (in the central)

Question 8

What are the neural connections for the thermoreceptors?

Answer 8

The receptors send afferent info to the thalamus. The thalamus relays the info to the hypothalamus, the Posterior Hypothalamus organizes response to cold and Anterior to hot. The Preoptic anterior hypothalamus integrates the amount of signals recieved from the anterior and posterior hypothalamus.

Question 9

What is the difference between the Eccrine and Apocrine sweat glands?

Answer 9

eccrine: has ACh (muscarinic) receptor (produces salty water to cool off)
apocrine: has NE/Ep (adrenegic) receptor (in the armpits and genitals) so produces viscous mucosal sweat which is smelly

Question 10

The Posterior pituitary gland releases?

Answer 10

• Vasopressin

- Oxytocin

Question 11

The Anterior pituitary gland releases?

Answer 11

• TSH
• ACTH
• Growth hormone
• LH
• FSH
• Prolactin

Question 12

What’s the signaling of hypothalamus, pituitary, peripheral tissues, and target cells?

Answer 12

Neuronal/ Hormonal Signal -> Hypothalamus Releases “Hormone 1” -> Anterior Pit Releases “Hormone 2” -> Gland/Tissue Releases “Hormone 3” –> Target Cells Provide Physiological Responses

Question 13

Explain the role of negative feedback in the hypothalamic-pituitary axis

Answer 13

The negative feedback is caused by the buildup of either hormone 2 or 3 which are secreted in response to the original neuronal signal and signals for the system to shutdown

Question 14

Shared characteristics of Multi-unit smooth muscle and Skeletal muscle

Answer 14

a nerve with a synapse is required to excite the cell and exist in a motor unit composition

Question 15

Shared characteristics of Single smooth muscle and Cardiac muscle

Answer 15

can generate their own AP and spontaneously depolarize (unstable resting MP) and function as a single unit

Question 16

Unique characteristics of Cardiac muscle?

Answer 16

Striated (1-2 nuclei, short and branching)

Question 17

Unique characteristics of Skeletal muscle?

Answer 17

Straited (multiple nuclei, long and cylindrical)

Question 18

Unique characteristics of Smooth muscle?

Answer 18

Non-straited

Question 19

Explain the concept of function syncytium and mechanistically describe the role of structures within cardiac intercalated discs that underlie this concept

Answer 19

Functional syncytium require electrical coupling (electrical synapse, connexin units in-between cells form connexin pores which electrically couple the cells) and mechanical coupling (desmosome has cadherins linked to keratins to adjacent cells, which physically synchronize them)
Cardiac muscle cells are electrically connected by gap junctions, this causes the entire myocardium to behave as a single unit

Question 20

List differences between myoblasts, myotubes, and myofibers and diagram their importance in muscle development

Answer 20

• Myoblasts: committed to the myogenic lineage stem cells, able to proliferate (mononucleated and no contractile ability)
• Myotubes: multinucleated cells (no contractile protein and unorganized sarcomeres) can grow but are unable to proliferate (no cell division)
• Myofibers: contractile protein and sarcomeres (development may stop)

Question 21

Describe muscle satellite cells and their role in muscle repair and explain why this process fails in muscular dystrophy

Answer 21

Satellite cells- line along the plasma membrane like a large nucleus near the myofiber nucleus. They can re-enter the cell cycle when they sense damage in the myofiber is damaged and dies. Satellite cells are necessary to reduce the amount of regeneration and prevent connective tissue from intercalating into the skeletal muscle from numerous rounds of regeneration

Question 22

Provide a detailed model of the mechanisms by which calcium induces cross-bridge formation

Answer 22

Regulatory components:
Tropomyosin: wraps around actin thin filaments
Troponin: bound over the myosin binding site on actin filaments
TnT: binds to tropomyosin
TnI: binds to the myosin’s binding site on actin
TnC: binds calcium
Troponin is released by Ca2+ binding to it. Myosin binds to actin and activation of ATP-ase allows the myosin hinge reach to contract and pull the thin filament (H and I shrink)

Question 23

Explain why a mutation in the protein dystrophin produces muscle degeneration

Answer 23

Contraction of the Z-disc is usually transmitted to dystrophin. W/o dystrophin, the cell no longer can handle this contractile stress and causes the cells to dies from tearing. This leads to the cycles of regeneration and degeneration seen in muscular dystrophy patients that eventually causes the intercalation of connective tissue and loss of the satellite cell population.