Physiology Midterm Lecture #1 Flashcards
Summation
the process of adding up postsynaptic potentials and responding to their net effect
(Occurs in the trigger zone)
Temporal summation:
occurs when a single synapse generates EPSPs so quickly that one is generated before other one fades
Spatial summation
occurs when EPSPs from several different synapses add up to threshold at an axon hillock
Presynaptic Inhibition
- releasesGABA
Prevents voltage-gated Ca2+ channels in synaptic knob (S) from opening and so little or no neurotransmitter is released
Functions of the Skeleton
- Support
2.Protection - Movement
- Electrolyte balance
– calcium and phosphate levels - Acid–base balance
6.Blood formation
Osteogenic cells
tem cells that give rise to most other types of bone cells
Osteoblasts
bone forming cells
– Found under the endosteum and periosteum on the bone surface
Osteocytes
osteoblasts that have become trapped in the matrix they deposited
Lacunae cavities where osteocytes reside
Canaliculi–channels connecting lacunae
Physiology of Osseous Tissue
- Metabolically active
- phosphorous
- calcium
Mineral Deposition (mineralization)
- Crystallization process
- Calcium, phosphate, and other ions are taken from blood and deposited in bone - hydroxyapatite
- osteoblast
Mineral Resorption
process of dissolving bone and releasing minerals into blood
-osteoclast
Hypocalcemia
deficient calcium in blood
- results in changes in membrane potentials (muscle spasms)
this is caused by vitamin D deficiency
Hypercalcemia
- excessive calcium levels results ion channels less responsive
What Parathyroid hormones maintain norm blood calcium concentration?
Calcitriol (most active from is VD) and calcitonin
Calcitriol raises blood by
increase of Ca by the small intestine
increases Ca by skeleton
kidney reabsorption of Ca
Calcitonin decreases blood by
secreting C cells of thyroid glands
Homeostasis
the ability to detect change,activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions
Claude Bernard (1813–78)
Noted fairly constant internal conditions
Walter Cannon (1871–1945)
Coined the term homeostasis
Negative Feedback
allows for dynamic equilibrium within a limited range around a set point
Heat-losing Mechanism
If too warm, vessels dilate in the skin and sweating begins
Heat-gaining mechanism
If too cold, vessels in the skin constrict and shivering begins
Homeostasis
Receptor
Integrating center
Effector
Receptor– structure that senses change in the body
Integrating (control) center– processes the sensory information, “makes a decision,” and directs the response
Effector
– cell or organ that carries out the final corrective action to restore homeostasis
Positive Feedback and Rapid Change
loop causes a self-amplifying cycle where a physiological change leads to even greater change in the same direction
birthing
Nervous system communication:
communicates by electrical and chemical means to send messages from cell to cell
Endocrine system communication:
communicates by means of chemical messengers (hormones) secreted into to the blood
CNS
Brain and spinal cord
– Enclosed by cranium and vertebral
column
PNS
all other nerves besides brain and spinal cord
Nerve
a bundle of nerve fibers(axons)
wrapped in fibrous connective tissue
Ganglion
a knot-like swelling in a nerve where neuron cell bodies are concentrated
Sensory (afferent) Division of the PNS
Carries signals from receptors to CNS
Somatic - carries signals from skin, muscles, joints
Visceral - “” heart, lungs
Motor (efferent) division of the PNS
carries signals from CNS to effectors
Somatic - ‘’ skeletal muscles
Visceral - carries signals to glands, cardiac and sm
Properties of a Neuron
Excitability- ability to respond to a stimuli
Conductivity- produce electrical signals to other cells
Secretion - secretes a neurotransmitter
Dendrites:
Primary site for receiving signals from Nucleus other neurons
Soma:
control center of neuron – aka cell body
Axon (nerve fiber)
Specialized for rapid conduction of signals to distant points
Synaptic knob (terminal button):
junction (synapse) with the next cell
Myelin Sheath
Formed by oligodendrocytes in CNS and Schwann cells in PNS
Electrophysiology
study of cellular mechanisms for producing electrical potentials and currents
Electrical Potential
a difference in concentration of charged particles between one point and another
-cells are polarized, more negative on the inside of the membrane than outside
Electrical Current
a flow of charged particles from one point to another
Resting Membrane Potential
due to the unequal distribution of ECF and ICF
- Ions diffuse down their concentration
gradient - Plasma membrane is selectively permeable
- Electrical attraction of cations (+) and anions (-) to each other
Characteristics of Actions potentials
- All or None
- Nondecremental - does not get weaker with distance
- Irreversible
Refractory Period
a few ms after it is difficult or impossible to stimulate that region. The period of resistance to restimulation
Absolute refractory period
no stimulus of any strength will trigger AP
last as long as inactivated Na+ gates are closed
Relative refractory period
Only very strong stimulus will trigger new AP,
last until hyper-polarization ends
Saltatory Conduction
signal seems to jump from node to node
Speed Conduction of Nerve Fibers
Diameter of fiber - large fibers have increased SA = more rapid signals
Myelin = faster signal conductions
What ions are more abundant inside and outside the cell?
K+ concentration is higher inside the cell
Na+ is higher outside the cell
