UNIT 8- HOMEOSTASIS Flashcards
What is the role of skin and mucous membranes?
- Form barrier between internal and external environments. Provide first line of defense from infectious agents
- Skin provides an insulation layer and limit heat energy loss
What is the role of musculo-skeletal system?
Acquisition, consumption of food and water, avoiding predation, avoiding extremes of climate change, processes related to reproduction
What 2 systems are primarily involved in regulating homeostasis?
Nervous system and endocrine system
What are the 2 main cell types of the CNS and what function do they provide? Which can divide and what can’t divide?
Neurons- conduct electrical signals, release chemical signals (CANNOT DIVIDE)
Glia- support cells of neurons (CAN DIVIDE)
What is the role of sensory neurons?
transmit impulses from sensory receptors to CNS (PNS to CNS)
What is the role of motor neutrons? What are the 2 subtypes?
transmit impulses from CNS to target organs (CNS to PNS)
Autonomic motor neurons - innervate target organs
Somatic motor neurons - reflexes and voluntary control of skeletal muscle
What is the role of association/interneurons?
located within CNS contribute to functions of the NS
Match the function to the correct neuron:
1. large dendritic tree, one main output axon
2. one axons branches into 2
3. 2 axons
4. no obvious axon
5. one axon
A. Anaxonic
B. Unipolar
C. Bipolar
D. Pseudounipolar
E. Multipolar
- Large dendritic tree, one main output axon = Multipolar
- One axon branches into 2 = Pseudounipolar
- 2 axons = Bipolar
- No obvious axon = Anaxonic
- One axon = Unipolar
What are the 2 types of glia found in the PNS and what are role do they each have?
- Schwann cells- myelinate
- Satellite cells- support function in sensory and autonomic ganglia
What are the 4 main types of glia found in the CNS and what role do they each have?
- Oligodendrocytes- myelinate
- Astrocytes- surround capillaries, part of BBB
- Microglia- phagocytose pathogens and cellular debris
- Ependymal cells- form epithelial layer of ventricles and central canal of spinal cord
What does the membrane potential represent?
difference in ion electric potential
Why is the RMP negative? (-70mV) What influences the distribution of cations?
Anions are fixed within the cell as they cannot penetrate the plasma membrane. These anions will attract cations which are capable of bypassing the plasma membrane to raise the membrane potential. Distribution of cations is influenced by the fixed anions within the cell
What do we mean when we say each cell acts as a tiny battery?
There is a positive pole outside the plasma membrane and a negative pole inside the cell
What does the Nernst equation allow us to determine?
The membrane equilibrium potential for a particular ion
What does membrane potential of -90mV represent? What would a more neg or more pos MP cause?
-90mV represents the equilibrium membrane potential of potassium, where the intracellular and extracellular potassium concentrations are kept STABLE.
Fixed anions inside the cell attract potassium (can easily bypass the plasma membrane) causing the extracellular conc. of potassium to be lower and the intracellular conc. to be higher.
In order to make reach stable concentrations:
More negative MP would cause K+ influx
Less negative MP would cause K+ efflux
RMP=EK true or false?
FALSE
What MP once reached causes Na+ channels to close?
MP of +30mV is the peak of depolarization, this is when Na+ channels will close and K+ channels will open in order for repolarization to occur and return to RMP
Does the size of depolarization affect the size or duration of the AP?
NO
size of depolarization DOES NOT affect the duration or size of the AP
ALL APs have the same amplitude
The AP will always reach +30mV then Na+ channels will close no matter the size of the stimulus
What is different about the AP of skeletal muscle? What causes myotonia?
depolarization is still driven by Na+ channels BUT the RMP is driven by Cl- permeability
Deficits in Cl- give rise to myotonia- muscles can’t relax after contraction
What role do myelinated axons play in the AP current?
myelinated axons allow AP current to jump between nodes of ranvier and therefore speeds up the transmission. They also save energy as the total ion influx is much LESS
During the absolute refractory period…
neuron is unable to respond to a stimulus of any intensity
What does cascade imply in homeostasis? What are the 3 steps of homeostasis? What are the similarities and differences between extrinsic and and intrinsic pathways?
Cascade implies step-wise procedure where one component activates the next. Cascade results in activation of clotting factors
3 steps of homeostasis:
1. vasoconstriction / vascular spasm
2. formation of platelet plug (reduce blood loss)
3. production of a web of fibrin proteins which penetrate and surround platelet plug (coagulation)
Similarities: both pathways convert fibrinogen into fibrin. Both are biochemical pathways that activate clotting factors. Both converge to common pathway at thrombin
Differences: initiation of intrinsic pathway occurs when factors inside blood are exposed to extracellular matrix outside blood vessels. Initiation of extrinsic pathway occurs due to factor release by damaged tissues (shorter pathway)
