Unit 3: Homeostasis Part 1 - Nervous and Excretory System

Question 1

Define homeostasis.

Answer 1

the physiological state in which internal physical and chemical conditions are kept in a range that is suitable for biological processes

Question 2

List the negative feedback mechanisms.

Answer 2

Stimulus, sensor (detects change), integrator (compares existing conditions with ideal conditions), effector (elements that act to return system to normal), response

Question 3

Distinguish between negative and positive feedback.

Answer 3

Negative feedback - stimulus causes a response that compensates for the change (e.g. sweating when cold, thermostat)
Positive feedback - stimulus creates response that further increases change; does not result in homeostasis and causes conditions to be unstable (e.g. contractions during childbirth)

Question 4

Define thermoregulation.

Answer 4

The regulation of internal temperature by negative feedback mechanisms

Question 5

What is a neuron?

Answer 5

A nerve cell capable of conducting nerve impulses

Question 6

What are dendrites?

Answer 6

Projections of cytosol that carry signals towards the nerve cell body

Question 7

Besides neurons, what other cell makes up the nervous system and what is its function?

Answer 7

Glial cells; structure and support

Question 8

List the 3 basic types of neurons.

Answer 8

sensory neurons (to the brain), interneurons, motor neurons (from the brain)

Question 9

List the 3 major roles of kidneys.

Answer 9

1. Remove waste
2. Balance blood pH
3. Maintain water balance

Question 10

What 3 functions does urine formation depend on?

Answer 10

Filtration (of blood into the nephron), reabsorption (from nephron to body), secretion (from bloodstream into nephron)

Question 11

Why does the Loop of Henle dip down into the medulla?

Answer 11

Since it has a high sodium content, when the descending loop of Henle (which is permeable to water but not salt) dips into the medulla, water is passively reabsorbed. In the ascending loop of Henle (which is permeable to salt but not water), sodium ions are reabsorbed back into the medulla (so the cycle can continue, and because now there is more water).

Question 12

Describe what happens in the proximal tubule.

Answer 12

• Na+, glucose and amino acids are actively transported
• Cl- and HCO3- passively transported due to attraction
• water passively transported due to osmosis
• H+ may be secreted to balance blood pH

Question 13

Describe what happens in the distal tubule.

Answer 13

• Na+ is actively transported if more water needs to be absorbed (it will follow through osmosis)
• H+ secreted to balance pH if necessary

Question 14

Describe what happens in the collecting duct.

Answer 14

• Na+ is actively transported if more water needs to be absorbed

Question 15

What is normal blood pH? Differentiate between acidosis and alkalosis.

Answer 15

Normal blood pH is 7.3 - 7.5.
Acidosis is when blood is too acidic; pH is too low.
Alkalosis is when blood is too basic; pH is too high.

Question 16

Explain what happens when osmotic blood pressure is too high.

Answer 16

• osmoreceptors in hypothalamus detect high osmotic blood pressure, causing hypothalamus cells to shrink and nerve signals sent to pituitary gland
• pituitary glands release anti-diuretic hormones into the blood, increasing water absorption
• feelings of thirst occur; drinking lowers osmotic pressure of blood
• cells swell and stops ADH

Question 17

Explain what happens when blood pressure is too low.

Answer 17

• the juxtaglomerular apparatus in the bowman’s capsule detects low blood pressure; specialized cells release renin
• renin converts angiotensinogen into angiotensin
• angiotensin causes construction of blood vessels and stimulates release of aldosterone from adrenal glands
• aldosterone is carried to kidneys and increases water and Na+ reabsorption (greater blood volume = higher pressure)

Question 18

Are osmotic blood pressure and typical blood pressure examples of negative or positive feedback?

Answer 18

Negative

Question 19

What is deamination?

Answer 19

When amino groups are removed from amino acids when proteins are broken down; the amino groups are then converted into ammonia and the rest of the amino acid is used for energy

Question 20

What are the 2 nervous systems and how are they different?

Answer 20

Central nervous system: brain and spinal cords; Peripheral nervous system: all other nerves, carrying info to and from CNS

Question 21

What are the 2 types of nerves in the peripheral nervous system and how are they different?

Answer 21

Somatic nerves (voluntary movements), Autonomic nerves (involuntary; organs like stomach, heart)

Question 22

What are the 2 types of somatic nerves and how are they different?

Answer 22

Sensory nerves (pick up & transport info. about environment; to the brain), Motor nerves (stimulate response; from the brain)

Question 23

What are the 2 types of autonomic nerves and how are they different?

Answer 23

Sympathetic (prepare body for stress); Parasympathetic (return body to normal after stress)

Question 24

What is a reflex arc?

Answer 24

A neural circuit that travels through the spinal cord but does not require coordination of the brain; resulting in an immediate “reflex” response

Question 25

Describe what a resting nerve cell looks like.

Answer 25

More Na+ on the outside of the membrane than K+ on the inside, resulting on a net positive on outside and net negative on inside; polarized

Question 26

What is a synapse?

Answer 26

The site at which neurons connect

Question 27

Describe what a stimulated nerve cell/action potential looks like.

Answer 27

Stimulus causes Na+ in the membrane to open, causing charge reversal; Na+ rush in and are attracted to negative charge further along the axon; disturbance causes more gates to open; depolarized

Question 28

Describe what a refractory nerve cell looks like (back to resting).

Answer 28

Na+ / K+ pumps restore original charge; repolarized

Question 29

What’s the difference between a pre-synaptic cell and a post-synaptic cell?

Answer 29

Pre-synaptic: neuron that transmits signal

Post-synaptic: neuron that receives signal

Question 30

Sympathetic nerves have ___ preganglionic nerves and ___ postganglionic nerves. Parasympathetic nerves have ___.

Answer 30

Sympathetic nerves have short preganglionic nerves and long postganglionic nerves. (Parasympathetic have opposite)

Question 31

Difference between chemical synapse and electrical synapse

Answer 31

In chemical synapse, neurotransmitters diffuse across synaptic cleft, binding to receptors in the plasma membrane of the post-synaptic nerve. In electrical synapse, pre- and post-synaptic nerves make direct contact and electric current is passed through a gap junction.

Question 32

What is acetylcholine and how does it work?

Answer 32

Acetylcholine is a neurotransmitter that once stimulated, must bee destroyed in order to allow the post-synaptic nerve to return to resting; the enzyme that destroys it is called cholinesterase

Question 33

What is a threshold level?

Answer 33

The minimum stimulus required to produce action potential in a nerve cell

Question 34

How does the brain distinguish between small and large stimuli?

Answer 34

impulse of greater frequency and more nerve cells stimulated

Question 35

What is alzheimer’s disease?

Answer 35

memory loss that affects daily function

Question 36

Which stage of the nerve cell has the most active pumps and why?

Answer 36

Refractory; Na+ and K+ must be pumped to return to resting position

Question 37

What is hyperpolarization?

Answer 37

When there is an even larger potential difference across the membrane, ensuring that the nerve cell DOES NOT carry the impulse (e.g. when you need one muscle to relax so the other can contract)

Question 38

What are catabolic reactions?

Answer 38

When waste materials are produced as the body breaks down complex molecules

Question 39

The ascending loop of Henle is permeable to ___, while the descending loop of Henle is permeable to ___.

Answer 39

ascending - permeable to salt

descending - permeable to water

Question 40

Hemodialysis vs. peritoneal dialysis

Answer 40

Hemodialysis: dialysis machine connected to vein, solute levels balance, waste removed
Peritoneal dialysis: dialysis fluid pumped into abdominal cavity; cavity membrane filters waste from blood (can be done at home)

Question 41

What is an example of positive feedback in the human body?

Answer 41

Childbirth; uterine contractions stimulate release of oxytocin, which further increases contractions

Question 42

What happens after neurotransmitter molecules

diffuse across the cleft and bind to receptors in the plasma membrane of the postsynaptic cell?

Answer 42

channels open allowing ions to flow, generating an impulse in the nerve cell

Question 43

What are the gaps between myelin sheaths called?

Answer 43

Nodes of Ranvier

Question 44

What is multiple sclerosis? (M.S.)

Answer 44

Myelin is attacked by the immune system, blocking/slowing the transmission, causing weak muscles, numbness, coordination issues

Question 45

Which feature of neurons ensures the one-way movement of action potentials?

Answer 45

The refractory period