Unit 2 Flashcards
What does the CNS contain
brain + spinal cord = decision maker
What does the PNS contain
cranial + spinal nerves = sense environment
Sensory division (PNS)
Somatic and visceral sensory nerve fibers that receive environmental input and deliver to the CNS
Motor division (PNS)
Motor nerve fibers that conduct impulses from the CNS to effectors (muscles)
Somatic nervous system (PNS)
Voluntary
Autonomic nervous system (PNS)
Involuntary
Sympathetic division (PNS)
Fight or flight
Parasympathetic division (PNS)
Conserve energy - rest and digest
What are the three fundmental types of neurons and their function
Sensory neurons: conduct signals from receptors to the CNS
Motor neurons: conduct signals from CNS to effectors
Interneurons: only confined to CNS
Neurons
Nerve cells that carry the signal
Neuroglia
Glial cells, “nerve glue” that provides support and structure
What are the properties of the neuron
- Excitability
- Conductivity
- Secretion
What are the steps of an action potential
- depolarization
- repolarization
- hyperpolarization
What is a magnitude or intensity that must be exceeded for a specific reaction to occur
threshold
Depolarization
Membrane potential moves towards 0 with fast voltage-gaited calcium channels opening up
Repolarizing
Membrane potential moves to be more negative - calcium channels are inactivated, and slow voltage-gated potassium channels open up
Hyperpolarization
Potassium channels start closing, but more potassium shifts out than needed. Na-K pump is used to switch Na and K around
What is it when a nerve cannot stimulate another action potential
Absolute refractory period
Relative refractory period
It takes more effort to stimulate an action potential
Myelination
Like insulation - conduction is fast and more accurate since axons have to travel less, only of node of ranvier
Satellite cells (PNS)
Help with dying or injured neurons
Schwann cells (PNS) and Oligodendrocytes (CNS)
Forms myelination on neurons and insulates neurons
Microglia (CNS)
Acts as macrophage
Ependymal cells (CNS)
Produce cerebral-spinal fluid and aid in neuro-regeneration
Astrocytes (CNS)
20-40% of cells. Form blood-brain barrier, provide nutrients, maintain ion balance, and remodel
What are the three types of activation
- ligand-gated
- mechanically gaited
- voltage-gaited
Synapses
Functional connection between a neuron and another cell
What are the types of synapses
- chemical: sends neurotransmitters across the synaptic cleft (indirect)
- electrical: connected by gap junctions to pass directly from neurons (direct)
Axodendritic synapses
The axon of the presynaptic neuron forms a synapse with the dendrite of the postsynaptic neuron
Axosomatic Synapses
The axon terminal of the presynaptic neuron interacts with the soma of the postsynaptic neurons
Axoaxonic synapses
The axon of one neuron forms a synapse with the axon of another neuron
Steps of synaptic signaling
- Action potential arrives at the presynaptic terminal, calcium channels open, and Ca²⁺ enters the terminal.
- Synaptic vesicles fuse with the membrane and release neurotransmitters.
- Neurotransmitters bind to receptors on the postsynaptic neurons.
- Ion channels open, causing excitability
- Neurotransmitters are terminated to stop the signal
- An action potential is triggered if the threshold is reached.
Soma
Maintains cell health and integrates incoming signals
Axon
Transmits electrical impulses from the cell body to the target cell
Axon Hillock
Initiates the action potential
Dendrites
Receive signals from other neurons
Axon Terminals
Release neurotransmitters to communicate with the next cell
Nodes of Ranvier
Gaps in the myelin where the signal is regenerated enable fast transmission
What are the muscle types?
- Smooth: in walls of hollow organs, involuntary, not striated
- Skeltal: In limbs, striated, voluntary
- Cardic: in heart walls, involuntary, striated
What is the function of muscles?
Produce movement, maintain posture, stabilize joints, generate heat
Five characteristics of muscle
- responsiveness
- conductivty
- contractility
- extensibility
- elasticity
Sacrolemma
Plasmid membrane that transmits electrical signal
Sarcoplasmic reticulum
Storage and transport of calcium
Triad and what it is composed of
Holds and store calcium
- terminal cisternae: pulls calcium and is a specific part of SR
- transverse tubule: connects electrical signal from sarcolemma to sarcoplasmic reticulum
Myofilaments
Made up of actin and myosin
Actin and myosin
What makes up myofilaments
Sarcoplasm
= cytoplasm, stores glycogen and myoglobin
Myofibrils
Composed of myofilaments
What is a muscle twitch
response of a muscle to a single, brief threshold stimulus –> a single contraction event
What are the three phases of a twitch
- Latent period: Preparing
- Period of contraction: increase in tension
- Period of relaxation: decrease in tension
Temporal summation
If another stimulus is applied before the muscle completely relaxes, tension increases. This could result in tetanus, where there is no relation
Motor units
Where one neuron interacts with multiple muscle fibers. The more motor units the higher the tension. (all or non-response)
How does relaxation occur?
- Nerve stimulation ceases - ACh is broken down, and acetylcholinesterase stops the signal to the sarcolemma
- Actively transport calcium back to SR
- Loss of calcium causes cytoplasm to dissociate from troponin, which causes tropomyosin to cover myosin binding sites
- Muscle fibers return to resting state
What is rigor mortis, and how does it occur?
- Calcium leaks out of muscle cells and binds to troponin
- Cross-bridge formation occurs until no ATP is available
- With no ATP myosin head can’t detach from action after the power stroke
- Muscle stays contracted till myofilament decays
Direct phosphorylation of ADP by creatine phosphate
1creatine:1ATP, last about 15 seconds. phospoho-cratine and ADP make creatine and ATP
Anaerobic pathway
1gluscose:2ATP, last about 30 seconds. Glucose breaks down to pyruvate, making lactic acid and ATP
Aerobic respiration (Krebs cycle)
1glucose:32-34ATP, last minutes to hours. Glucose and oxygen produce ATP and fatty acids
White meat makes…
fast glycolytic muscle - low in myoglobin high in glycogen
Red meat makes…
Slow oxidative muscle - high in myglobin
Axial skeleton versus appendicular skeleton
Axial: protects, supports, and carries body parts (skull, ribs)
Appendicular: aids in movement and manipulation of the environment (limbs, femur, scapula)
What are the three types of cartilage?
- elastic: very stretchy (external ears, epiglottis)
- Hyaline: flexible (nose, joints, stermum)
- Fibrous: thick collagen fibers that absorbs impact (knees)
Epiphysis
End of the bone
Diaphysis
Shaft of the bone
Osteoblasts
Produce bone matrix and secrete collagen
Osteocytes
They are found in the lacunae and were organized osteoblast but have matured. Monitor bone health
Bone lining cells
Monitor bone health - are found outside of the bone
Osteoclasts
Cells responsible for bone resorption and remodeling of the bone - closely related to macrophage
Osteogenic cells
Produce the next generation - can turn into osteoblasts, bone lining cells, or osteocytes
How do bones form?
Endochondral ossification: turning hyaline bones into long bones
Intramembranous ossification: the process of bone development from fibrous membranes
How do bones change in size?
lengthening and thickening
