Homeostasis and the nervous system

Question 1

What happens when BG concentration increases above norm?

Answer 1

STIMULUS: Blood glucose concentration rises above normal.
RECEPTOR: Islets of Langerhans in the pancreas are stimulated.
CORRECTIVE MEASURES: The islets of Langerhans secrete
insulin into the bloodstream. Blood transports the insulin to
the liver and muscles. Insulin increases the permeability of the cell surface membrane to glucose. Glucose is absorbed more quickly by the cells.
Insulin causes the liver and muscles to convert excess glucose to glycogen. Glycogen is stored in the liver and muscles.
Blood glucose concentration decreases. This provides a feedback to the receptor to reduce insulin production.

Question 2

What happens when BG concentration decreases below normal?

Answer 2

STIMULUS: Blood glucose concentration falls below normal.
RECEPTOR: Islets of Langerhans in the pancreas are stimulated.
CORRECTIVE MEASURE: The islets of Langerhans secrete glucagon into the bloodstream.
Blood transports the glucagon to the liver and muscles.
Glucagon causes the conversion of stored glycogen back to glucose.
From the liver, glucose enters the bloodstream.
Blood glucose concentration increases. This provides a feedback to the receptor to decrease glucagon production.

Question 3

What happens when W.P of blood increases?

Answer 3

RECEPTOR: Hypothalamus stimulated
CORRECTIVE MECHANISM: Less ADH released by pituitary gland into the bloodstream. Less ADH transported to the kidneys. Cells in the walls of the collecting ducts become less
permeable to water. Less water reabsorbed into the bloodstream More water excreted. Urine is more diluted. More urine produced.

Question 4

What happens when water potential of the blood decreases?

Answer 4

RECEPTOR: Hypothalamus is stimulated.
CORRECTIVE MECHANISM: More ADH released by pituitary gland into the bloodstream. More ADH transported to the kidneys. Cells in the walls of the collecting ducts become more permeable to water. More water reabsorbed into the bloodstream. Less water excreted. Urine is more concentrated. Less urine produced

Question 5

What happens when human body temperature begins to rise above norm?

Answer 5

RECEPTOR: Hypothalamus- sends nerve impulses to Sweat glands, Arterioles. Metabolism

S: Sweat glands become more active, resulting in increased production of sweat. As more water in the sweat evaporates from the surface of your skin, more latent heat of vaporisation is lost from your body.
A: Dilation of ar terioles in your skin and constriction of shunt vessels allow more blood to flow through blood capillaries in your skin. This allows more heat to be lost through your skin by radiation, convection and conduction.
M: Decreased metabolic rate, to reduce the amount of heat released within your body.

Question 6

What happens when human body temperature begins to fall below norm?

Answer 6

RECEPTOR: Thermoreceptors send nerve impulse to hyp and hypothalamus.
CORRECTIVE MECHANISM:
S: Sweat glands become less active, resulting in decreased production of sweat. As less water in the sweat evaporates from the surface of your skin, less latent heat of vaporisation is lost from your body.
A: Constriction of your skin ar terioles and dilation of shunt vessels so that less blood flows through blood capillaries in your skin. This reduces the heat lost by convection, radiation and conduction.
M: Increased metabolic rate, to increase the amount of heat released within your body.
**When the above reactions are not sufficient to prevent a drop in body
temperature, ‘shivering’, a reflex contraction of your body muscles,
occurs. This spasmodic contraction of the skeletal muscles increases the amount of heat released and helps to raise your body temperature to normal.

Question 7

What happens when your hand touches a hot object?

Answer 7

1. The heat on the object stimulates the nerve endings (receptors) in your skin.Nerve Impulses are generated.
2. The nerve impulses travel along the sensory neurone to your spinal cord.
3. In your spinal cord, the nerve impulses are transmitted first across
   a synapse to the relay neurone, and then across another synapse to the motor neurone.
4. The motor neurone transmits the impulses from the spinal cord to the effector. (MUSCLE/GLAND)
5. Your biceps muscle (effector) then contracts and causes your hand to withdraw suddenly.