ANATOMY MUSCLES + NERVOUS SYSTEM

What are the three types of muscle tissue?

Skeletal, Cardiac, Smooth

Which muscle type is voluntary and striated?

Skeletal muscle

Which muscle type is found in the heart?

Cardiac muscle

What are the main functions of skeletal muscle?

Movement, posture, support soft tissues, guarding entrances/exits, heat generation

What connective tissue surrounds the whole muscle?

Epimysium

What connective tissue surrounds muscle fascicles?

Perimysium

What connective tissue surrounds individual muscle fibers?

Endomysium

What organelle stores calcium in skeletal muscle?

Sarcoplasmic reticulum (SR)

What are T-tubules responsible for?

Transmitting the action potential into the muscle fiber

What neurotransmitter is released at the neuromuscular junction?

Acetylcholine (ACh)

 What triggers the release of calcium from the SR?

Muscle action potential

What is the role of calcium in muscle contraction?

Binds to troponin, allowing actin-myosin binding

What causes the muscle to relax?

 Calcium is pumped back into the SR and ACh is broken down

What are the three phases of a muscle twitch?

Latent period, contraction phase, relaxation phase

What is motor unit recruitment?

Increasing the number of active motor units to produce stronger contractions

What are the three ways muscles generate ATP?

Creatine phosphate, anaerobic glycolysis, aerobic respiration

 What are the characteristics of slow oxidative (SO) fibers?

Slow contraction, high endurance, many mitochondria

Which fiber type is used for sprinting?

Fast oxidative-glycolytic (FOG) and fast glycolytic (FG)

What is the difference between isotonic and isometric contraction?

Isotonic changes muscle length, isometric does not

What are the parts of a sarcomere?

Z-disc, A-band, I-band, H-zone, M-line

What are the two main divisions of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

What are the three functional divisions of the PNS?

Somatic, autonomic, enteric

What are the parts of a neuron?

Soma (cell body), dendrites, axon, axon terminal

What carries signals toward the cell body?

Dendrites

What is the function of Schwann cells?

Myelinate axons in the PNS

Which neuroglia form the blood-brain barrier?

Astrocytes

What is the difference between graded and action potentials?

Graded are local and variable; action potentials are all-or-none and travel long distances

What causes depolarization during an action potential?

Influx of Na⁺ ions

What causes repolarization?

Efflux of K⁺ ions

 Where do action potentials begin?

Axon hillock

 What is saltatory conduction?

Jumping of action potential between nodes of Ranvier on myelinated axons

What is a synapse?

The junction between neurons or between a neuron and another cell

What happens at a chemical synapse?

Neurotransmitters cross the synaptic cleft to bind to receptors on the postsynaptic cell

 Can CNS neurons regenerate?

Rarely, due to limited environment for regrowth

What helps PNS neurons regenerate?

Schwann cells

Which of the following is not a function of skeletal muscle?
 A. Heat production
B. Pumping blood
C. Movement
D. Maintaining posture

B. Pumping blood – That’s the job of cardiac muscle, not skeletal.

The connective tissue that surrounds a muscle fascicle is:
A. Epimysium
B. Endomysium
C. Perimysium
D. Myomysium

C. Perimysium – This surrounds fascicles (bundles of muscle fibers)

What ion is critical for initiating muscle contraction?
A. Potassium
B. Sodium
C. Magnesium
D. Calcium

D. Calcium – Calcium is essential for triggering contraction by binding to troponin.

During isometric contractions:
A. The muscle shortens
B. The muscle lengthens
C. Tension increases but length stays the same
D. The muscle relaxes

C. Tension increases but length stays the same – That’s the definition of an isometric contraction.

Which muscle fiber type is most resistant to fatigue?
A. FG
B. FOG
C. SO
D. All are equal

C. SO (Slow Oxidative) – These are fatigue-resistant, built for endurance.

What neurotransmitter is released at the neuromuscular junction?

Acetylcholine (ACh) – The neurotransmitter released into the synaptic cleft at the NMJ.

Describe the role of the sarcoplasmic reticulum in muscle contraction.

Sarcoplasmic reticulum stores and releases calcium ions (Ca²⁺), which initiate contraction by allowing actin and myosin to bind.

Name the three phases of a muscle twitch as seen in a myogram.

Latent period, Contraction phase, Relaxation phase

What is motor unit recruitment and why is it important?

Motor unit recruitment is the activation of more motor units to generate greater force in a muscle. It allows for graded control of strength.

Explain the difference between concentric and eccentric contractions.

Concentric: muscle shortens while contracting (e.g., lifting a weight).
Eccentric: muscle lengthens while contracting (e.g., lowering a weight).

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Which neuroglial cell forms myelin in the CNS?
 A. Schwann cell
B. Astrocyte
C. Oligodendrocyte
D. Microglia

C. Oligodendrocyte – Myelin in the CNS.

Which part of the neuron receives incoming signals?
A. Axon
B. Dendrite
C. Axon terminal
D. Soma

B. Dendrite – Receives signals and sends them to the cell body.

Graded potentials occur:
A. Only in axons
B. At the synaptic cleft
C. In the dendrites and soma
D. Only in myelinated neurons

C. In the dendrites and soma – Graded potentials occur in receptive regions.

Action potentials travel faster in:
A. Unmyelinated axons
B. Dendrites
C. Cell bodies
D. Myelinated axons

D. Myelinated axons – Saltatory conduction is faster than continuous conduction.

Which glial cells help circulate cerebrospinal fluid?
A. Astrocytes
B. Ependymal cells
C. Oligodendrocytes
D. Microglia

B. Ependymal cells – These line ventricles and produce/circulate CSF.

List the steps in generating an action potential.

Resting membrane potential

Stimulus → reaches threshold

Depolarization: Na⁺ channels open

Repolarization: K⁺ channels open

Hyperpolarization

Return to resting potential

What is saltatory conduction?

Saltatory conduction is when an action potential jumps from one node of Ranvier to another in a myelinated axon, speeding up transmission.

Name two differences between the CNS and PNS in terms of neuron repair.

CNS: Limited repair due to lack of growth factors and glial scar formation
PNS: Schwann cells promote regrowth if soma is intact

What are the three functional classifications of neurons?

Sensory (afferent), motor (efferent), and interneurons

What happens at a chemical synapse?

Chemical synapse: Neurotransmitters are released from presynaptic neuron → cross synaptic cleft → bind to receptors on postsynaptic cell → graded potential generated

Z-disc

boundary of sarcomere

M-line

middle line holding thick filaments together

I-band

 thin filaments only, spans two sarcomeres

A-band

full length of thick filaments, includes some overlap with thin

H-zone

center of A-band, thick filaments only (no overlap)

A patient has damage to the motor neurons innervating their leg. What effects would you expect in the skeletal muscle of that leg over time?

Muscle atrophy due to lack of stimulation; possible loss of voluntary movement and reflexes.

During a sprint, your muscles feel a burning sensation. What’s happening at the cellular level?

Anaerobic respiration is occurring due to lack of oxygen, causing lactic acid buildup in fast glycolytic fibers.

If a drug blocks ACh receptors at the neuromuscular junction, what would happen to muscle contraction?

Muscle contraction would be inhibited; ACh cannot bind, so the muscle fiber cannot depolarize.

A person is exposed to a toxin that keeps calcium channels open in the sarcoplasmic reticulum. What happens?

Continuous muscle contraction (tetanus), since Ca²⁺ stays in the cytoplasm and actin-myosin cross-bridges keep forming.

An athlete lifts a heavy weight and their muscle doesn’t change length, but tension increases. What type of contraction is this?

Isometric contraction

Why do marathon runners have more slow oxidative (SO) fibers than sprinters?

SO fibers are fatigue-resistant and efficient at aerobic respiration, ideal for endurance events.

Why do action potentials travel faster in myelinated neurons compared to unmyelinated ones?

Saltatory conduction allows APs to jump from node to node, increasing speed.

A patient has multiple sclerosis (MS), which demyelinates axons. What symptom might this cause?

Slower neural conduction, leading to muscle weakness, poor coordination, and sensory problems.

 A person accidentally touches a hot stove and instantly pulls their hand back. What type of neural circuit is involved?

Reflex arc — involves sensory neuron → interneuron → motor neuron without higher brain involvement.

If a person has a spinal cord injury that severs lower motor neurons, what happens to the muscles below the injury?

Flaccid paralysis — muscles cannot contract due to loss of neural input.

Why might a person with low ATP levels (e.g., during extreme fatigue or mitochondrial disease) experience muscle cramping?

ATP is required to detach myosin heads from actin — without it, cross-bridges stay locked (cramp or rigor).

A drug inhibits acetylcholinesterase (AChE). What effect will this have at the neuromuscular junction?

 ACh will not be broken down → prolonged stimulation of muscle fiber → continuous contraction/spasms.

In cardiac muscle, what ensures rhythmic contractions without neural stimulation?

The presence of pacemaker cells and gap junctions that allow electrical signal propagation between cells.