Exam 1 Flashcards
Homeostasis
-Maintenance of internal conditions in face of external perturbations
-maintaining a dynamic steady state of internal environment
-normal set point for physiologic parameters
Homeostatic control
- Body detects deviations from normal
- Integrate information with needs of the body
- Respond by adjusting or adapting to restore homeostasis
Homeostatic control can be ___ or____
Local, systemic
Homeostatic control is always
Coordinated by feedback/feedforward loops
Homeostatic factors
-pH
-Fluid volume and pressure
-Temperature
-H2O, salt/electrolytes
-Waste products
-O2 and CO2
-Nutrients
Negative feedback loop
- Sends a signal back to the stimulus, reducing the intensity of the stimulus
- Bringing the body closer to homeostasis
Examples of negative feedback loops
- Appetite
– Hormones
– Blood glucose
– Thermoregulation (at the level of the skin)
Positive feedback loops
-Sends a signal back to the stimulus, increasing the intensity of the stimulus
-Pushes the body farther away from homeostasis, as a means to an end
Examples of positive feedback loops
• Parturition
• Hormones
• Blood clotting
• Lactation
Feedforward loops
• An anticipatory response
– Precedes a stimulus
– Can be preventative
Examples of feedforward loops
– Salivation
– Motor control
– Anxiousness
– Lactation
What do cells do?
• Acquire things (uptake)
• Build things (synthesis)
• Converts things (metabolism)
• Reproduces (proliferates)
• Dies (apoptosis)
Nucleus
– Control center
– Houses DNA
– Site of transcription
– DNA to mRNA
Endoplasmic reticulum
- Rough
– Studded with ribosomes
Ribosomes
- Site of translation
– mRNA to protein
Golgi apparatus
– Takes proteins from ER
– Post-translational modification
• Activates proteins
– Works with vesicles to package p
Phospholipids
• Phosphate head (-)
– Hydrophilic
• Lipid (long fatty acid chains) tail (neutral)
– Hydrophobic
Cholesterol
• Between phospholipids
• Fluidity/flexibility
• Reduce permeability
Membrane protein receptors
• Bind specific ligands
• Cause intercellular response
• Open/close channel
• Promotes endocytosis
Examples of chemical messengers
- paramones
- hormones
- neurotransmitters
Paramones
Local (interstitial space)
• Histamines, cytokines, growth factors
Hormones
• Systemic (bloodstream)
• Multiple target tissues
• Insulin, FSH, GH
Neurotransmitters
• Neuronal cells after synapse
Examples of passive transport
- Facilitated diffusion
- Simple diffusion
- Osmotic diffusion
Simple diffusion
- O2, CO2
– Move down concentration gradient
Facilitated diffusion
-Permitted movement down gradient
– Ions, AA, CHO
Active transport
– Independent of gradient
• Na+/K+ ATPase Pump
• Requires energy
– leak, ion gated, ligand gated
Chemical gradient
One molecule occurs at higher
concentration on one side of the
membrane
Electrical gradient
Charged molecule occurs a higher
concentration on one side of
membrane
Electrochemical gradients
Chemical and
electrical gradients exist at the same
time
Membrane potential
– Difference in electrical voltage in ECF and ICF
OR
– Separation of charges across membrane
• Na+, K+ Cl-, intracellular proteins –
• harness potential energy
Polarity of membrane
- Negative on inside
- positive on outside
Only _____ cells respond to changes in potential
Excitable
Resting potential is established by
- sodium- potassium pump
- 3 Na out, 2 K in
Electrochemical gradient
– + outside
– - inside
Na+ concentration gradient
Pumped out, stays out
K+ concentration gradient
– Pumped in, flows out
– Equilibrates with electrical gradient
~ -70 to -90 mV
For resting potential:
Electrochemical gradient flows ___, Na concentration gradient flows ____, and K concentration gradient flows _____
Outside in, outside in, inside out
Membrane potential steps
- Stimulus
- Depolarization
- Repolarization
4.Refractory period
Stimulus (membrane potential)
Potential rises above threshold (from -90 to -55 mV)
Depolarization
• Voltage-gated Na channel open, Na rushes in (down conc. Gradient)
• Charges reversed (+30mV)
• Adjacent Na channels open
Repolarization
• Na channels lock
• Voltage-gated K channels open, K rushes out
• Charges reversed again
Refractory period
• K channels close & lock
• No more action potential
• Na/K ATPase restores resting potential
Action potential in endocrine cells
• Excretion of pre-packed vesicles (exocytosis)
– Hormones, enzymes
Action potential in muscle cells
• Opens Ca channels on membrane/sarcoplasmic reticulum
– Muscle contracts
Action potential in neuronal cells
• Secretion of neurotransmitters
– Norepinephrine
– Acetylcholine
Cell body of neuronal cells
Soma, nucleus and organelles
Dendrites
Somal branches
Receives upstream signals
Axon
• Tubular extension/tail
• Transmits signal downstream
• Starts at axon hillock (base of tail)
• Travels to axon terminal (tip of tail)
• Causes neurotransmitter release
Myelin coat/sheath
Intermittent lipid cover
Axons are formed by _____
Non-neuronal support cells
Schwann cells are found in
Peripheral nerves
Oligodendrocytes are found in the
Central nervous system
Nodes of Ranvier
Bare axon surface where action potential is generated/propagated
Saltatory conduction
Action potential skips over myelinated areas
– Increases propagation speed by reducing “stops”
– Requires less Na and K movement
• Less ATP needed to restore concentration gradients with Na/K Pump
Synapse
Point where information is passed
Synapse is the association between ___ and _____
Axon terminal and target (excitatory) cells
Synaptic cleft
Space between knob and target cell
Synaptic knob
• Bell-shaped ending of axon
• Contains synaptic vesicles
Synaptic vesicles in chemical transmission
Packaged neurotransmitters
In chemical transmission ____ causes ____ to open, causing _____
Action potential, Ca channels, exocytosis
During chemical transmission ____ move across the cleft causing receptors to bind to ______
Neurotransmitters, target cell
Action potentials move from
Pre synaptic to post synaptic cells
Role of glial cells
• Structure
• Protection
• Nourishment
Astrocytes
– In CNS
– Help organize neurons
– Deliver nutrients, clear neurotransmitters, balance ions
Oligodendrocytes
– Myelinate axons in CNS
Schwann cells
– Myelination axons in PNS
Ependymal cells
– Line brain ventricles/central canal
– Produce cerebrospinal fluid (CSF)
• Surface cilia circulate CSF
Microglia
-Phagocytic cells
• Remove invading organisms
Neurons make up ___ of total cells in the brain
10%
Spinal cord
– Passageway between brain and body
– Coordination of some basic reflexes
– Source of motor nerves
– Destination of sensory nerves
Meninges
CNS wrapping membranes
Dura mater
– Tough, outmost layer
– Has sinuses where blood and CSF recombine
Arachnoid mater
– CSF-filled middle layer
– Villi project into dura sinuses for CSF transfer
Pia mater
– High vascular inner layer
– Includes cells that form CSF
Brain capillaries have ____ junctions
Tight
Molecules that can pass through brain capillaries
• Lipid-soluble particles
-O2, CO2, steroids, alcohol
• Membrane-bound protein carriers
-HIGHLY selective
-Glucose, AAs, ions
Cerebral spinal fluid
Cushions brain (and spinal cord) & provides nutrients
Cerebrum
– Largest area of the brain
– Highest complexity
– Highest thought
• Consciousness
• High degree of educability
Cerebral cortex
Outermost tissue
Gray matter
• Cell bodies/dendrites
• Vasculature
White matter
• Bundles of myelinated axon fibers
• “tracks” for neural pathways
Occipital lobe
Visual processing cortex
Temporal lobe
Auditory cortex
Parietal lobe
• Somatosensory cortex
• Body position
Primary motor cortex
Initiate movement
Supplementary motor complex
Coordinating movement
Premotor complex
Planning movement/problem solving
Broca’s area
Frontal lobe
• Articulation/execution of speech
• Based on information from Wernicke’s area
Wernicke’s area
Temporal lobe
• Articulation/execution of speech
• Based on information from Wernicke’s area
Hippocampus
• Learning and memory
Olfactory bulb
Smell
Basal nuclei
Motor control and executive functions
Vestibulocerebellum
• Maintains balance
• Controls eye movement
Spinocerebellum
• Coordinates w/ cerebral cortex for motor control
• Predicts body position
Cerebrocerebellum
• Majority of cerebellum
• Lower voluntary action
• Some procedural memories
Brain stem
• “lowest”/least complex function
– Sleep/wake, alertness, basic touch/pressure
– Systems activity
Medulla
– Swallowing, salivation
– Vomiting (CTZ)
– Respiration
– Blood pressure
– Heart rate
Pons
– Changes in RR and BP
– Analgesic system, sleep
Midbrain
Motivation
Spinal cord contains
– White & gray matter
– Meninges
– CSF
Spinal withdrawal
Withdrawing body part from damaging sources
Spinal stretch
Contracting skeletal muscle to counteract stretch
Crossed extensor reflex
Shifts load from injured limb to other
sensory nerves
afferent division
-detect conditions in body tissues
-alert CNS
motor nerves
efferent division
-begins in CNS
-terminate in target tissues (excitable cells)
somatic division
voluntary
autonomic division
involuntary
sensory nerves (3)
-receptor/dendrite
-axon
-cell body
receptor/dendrite
-Receptor near dendrite tips
-Receptor part of dendrite tips
-Affect axon hillock potential
axon
-Connects to dendrites
-Carries signal to CNS (via action potential)
cell body
-Axon “offshoot”
-Skips depolarization during action potential
-Groups located in dorsal root ganglia
Sensory nerve receptor types
-Photoreceptors: light
-Mechanoreceptors: stretch/bending
-Thermoreceptors: heat/cold
-Osmoreceptors: ECF molarity
-Chemoreceptors: detect chemicals
-Taste/smell
-O2/CO2 in blood
-Nutrients in GI tract
-Nociceptors: pain
the intensity of sensation in nerve receptors is determined by _______
action potential amount
frequency code
1 neuron stimulating another over and over
population code
several neurons stimulating an action/working against one another
tonic receptors
gradual adaptation (ex. Muscle stretch receptors)
phasic receptors
rapidly adapt (ex. Odor, touch, temperature)
ANS efferent motor division: voluntary
Short preganglionic neurons originate in _________
and their correlating neurotransmitter is _______
middle of the spinal cord
acetylcholine (ACh)
ANS efferent motor division: voluntary
Long preganglionic neurons originate from ________
and their correlating neurotransmitter is _______
ganglion to target
norepinephrine (NE)
ANS efferent motor division: involuntary
Short preganglionic neurons originate in _________
and their correlating neurotransmitter is _______
ganglion to target
acetylcholine (ACh)
ANS efferent motor division: voluntary
Long preganglionic neurons originate in _________
and their correlating neurotransmitter is _______
brain stem or low spinal cord
acetylcholine (ACh)
Somatic nervous system (SNS)
-motor neurons
-one-neuron “chain”
-originate at ventral horn of spinal cord
-axon is continuous to skeletal muscle
SNS stimulates the ______ ONLY
skeletal muscle
