Download Dynamic Equilibrium Review 1. Describe the structure and function

Dynamic Equilibrium Review
1. Describe the structure and function of each component of a typical neuron.
Dendrites – receive signal from other neurons or outside world (senses)
Cell body – site of metabolic activity, most typical cellular processes happen here
Axon – long strand branching off cell body, carries signal away from cell body
Myelin sheath – made of Schwann cells, “insulates” the axon from ion exchange
Axon terminals – branches off axon, release neurotransmitters into synapse to pass
signal onto the next cell
2. When looking at the relative ion levels inside and outside a cell, what do we notice?
How does this important to a neuron?
The outside of the cell is more positive, relative to the inside. This assists in ion
exchange (Na+ in, K+ out) that is the process of neuron firing.
3. How is both passive and active transport part of the function of a neuron?
Sodium will rush in once the ion channels open (when the threshold potential is
reached) without the assistance of energy – passive. It is active when the Na+/K+ pump
forces sodium back out of the cell, using ATP in the process – active.
4. What is the difference between the resting, threshold and action potentials?
Resting: -70mV, voltage that neurons exist in when not “firing”
Threshold: -50mV, voltage required to open the Na+ channels
Action: not a specific potential, but the rapid change from -50 mV, to +30 mV, then back
to -80 mV during the neuron firing
5. Explain the role of ion exchange in neuron conduction.
Na+ will rush into the cell first, then K+ will rush out (at exposed regions of the axon
called nodes) because of electrical and concentration gradients.
6. How does the signal at the end of one neuron reach the next?
Neurotransmitters are expelled from the axon terminal into synapse, attach to receptors
on dendrites of next cell, then are taken back into the axon terminals they came from.
7. How do stimulants and depressants act differently on the nervous system?
Stimulants will increase ATP production, increasing alertness, depressants do the
opposite. Not to be confused with excitatory neurotransmitters (encourage neuron
firing) and inhibitory neurotransmitters (prevent neuron firing).
8. What would typically make a drug highly addictive?
If it activates the rewards centre.
9. What is the difference between the CNS and PNS?
The CNS is the processing and decision making centre. Consists of brain and spinal
cord. PNS is sensory input and motor output.
10. Explain how you can break down the PNS into smaller systems.
First into somatic (conscious control, like moving your arm) and autonomic (involuntary
like your heartbeat and digestive system). Autonomic is further broken down into
sympathetic (increase heart rate, breathing, pupil dilation – think of being scared) and
parasympathetic (the exact opposite).
11. What is the role of the endocrine system? How does the role of hormones differ
from that of neurons?
It is critical in maintaining homeostasis (body temp, blood pH and glucose levels, thirst
and hunger, etc). The effects tend to be more long lasting than neurons and reach
every cell instead of a select few.
12. Although they sound similar, the endocrine and exocrine glands have quite different
roles. Why is this? (Bonus: how does a paracrine gland work?)
Exocrine gland release their secretions into body cavities and onto surfaces (tear ducts,
sweat glands, etc). Endocrine glands release their secretions into the bloodstream.
13. Why is the pituitary gland considered the “master gland”?
Because its secretions affect then action of other glands (though it often gets its orders
from the hypothalamus…)
14. Explain the insulin/glucagon system in terms of a feedback mechanism.
When blood sugar is high, insulin is released from beta islets cells on the pancreas.
This tells all cells to increase the absorbance of glucose, AND tells the liver to form
glycogen from excess glucose. When blood sugar is low, glucagon (from alpha cells
of the pancreas) goes to the liver, encouraging it to break down glycogen into
glucose.
15. Explain the roles of FSH and LH in the sexual maturing of a male or female.
Both hormones affect the same set of precursor cells in a 7 week old fetus. In males,
these cells differentiate into the testes and penis, in females into ovaries and the
clitoris.
16. What is the definition of menopause?
12 consecutive months without menstruation (a period).
17. If the ovaries go through meiosis, why are there not four eggs being released each
month?
Because of uneven cytokinesis. The majority of the cellular material moves to one side,
creating one large daughter cell and one tiny cell. The three small daughter cells are
called polar bodies.
18. What are the four phases, in order, of the menstrual cycle? What happens in each
phase?
Follicular – estrogen and FSH stimulate meiosis in one follicle. This creates a haploid
ova and three polar bodies. The uterine lining begins to thicken.
Ovulation – Follicle sac ruptures, releasing ova into Fallopian Tube.
Luteal – Ruptured follicle turns into yellowish structure called corpus luteum. Releases
progesterone to maintain uterine lining stability.
Menstruation – With no implanted zygote, corpus luteum falls apart, uterine lining
destabilizes and is shed over a period of 3- days.
19. Why does fertilization have to happen in the Fallopian tubes?
The sperm will capacitate here, By doing so, the sperm is more venerable and would
not be able to survive in the uterine environment.
20. What happens to the fertilized egg as it moves towards the uterus? What is each
new structure called?
This will not be on the test…
21. Why does the egg implant in the uterine lining as opposed to just attaching to the
surface?
It needs to be bathed in the fluid to receive nutrients and expel waste.