Nerve and Muscle

Question 1

Four General Types of Tissue

Epithelial

Connective

Muscle

Nerve

Answer 1

• Epithelial tissue: constitues the various organs of the body; come in many shapes and sizes
• Connective tissue: helps anchor or suppor the various structures of the body; cartilage, bone, collagen, etc.
• Muscle tissue: skeletal (voluntary) and cardiac (involuntarty)
• Nerve tissue: constitue the nervous system; transmit signals at lightening speeds across the body

Question 2

Inside and Outside Cell [ion]

K⁺

Na⁺

Cl^-

HCO₃^-

Resting Condition

Answer 2

• K⁺: 120-140 mM (in); 5 mM (out)
• Na⁺: 10-15 mM (in); 150 mM (out)
• Cl^-: 5-40 mM (in); 130 mM (out)
• HCO₃^-: 12-25 mM (in); 25 mM (out)
• Resting condition: High [K⁺] and low [Na⁺]

Question 3

Potassium Ion and Sodium Ion

Answer 3

• K⁺ will diffuse out of the cell
  
  • Generates partial negative charge in the cell
  • Diffusion power is greater than the electical force
• [K⁺] is maintained with potassium/sodium pump
• After a nerve is stimulated, Na⁺ rushes into the cell; permability for Na⁺ increases as nerve is stimulated
  
  • Generates partial positive inside and partial negative outside

Question 4

Threshold Potential

Depolarization

Repolarization

Hyperpolarization

Answer 4

• Threshold potential is the threshold that must be exceeded to generate an action potential
• Depolarization is the transient reduction in the membrane potential; opening of Na⁺ gates
• Repolarization occurs after reaching equilibrium for Na⁺; Na⁺ gates close and K⁺ gates open and K⁺ pours out of the cell
• Hyperpolarization occurs when the cell overshoots, and becomes hyperpolarized because K⁺ gates are slow to close; Na⁺/K⁺ pump brings back to equilibrium

Question 5

Action Potential Diagram

Answer 5

Question 6

Myelin and its Function

Answer 6

• Myelin is a special coating on nerves that speeds up signal transduction
• Space between two myelinated sections is n__ode of Ranvier; high density of Na⁺ channels
• Glial cells myelinate nerves
  
  • Oligodendrocytes in CNS
  • Schwann cells in PNS

Question 7

Saltatory Conduction

Answer 7

• Saltatory conduction is when the nerve impulses jump from node of Ranvier to node of Ranvier
  
  • This hastens signal transduction

Question 8

Neuromuscular Junction

Answer 8

• At the neuromuscular junction, acetylcholine (ACh) is synthesized and released from the terminal button, through the synaptic cleft, and is bound to ligand activated channels on the postsynaptic membrane that allow Na⁺ to enter
• ACh is broken down to acetate and choline by acetlycholinesterase
  
  • Occurs at the postsynaptic membrane

Question 9

EPSPs and IPSPs

Answer 9

• When a synaptic connection between two neurons is “exciting,” such that the same number of action potentials is passed from neuron 1 to neuron 2, it is known as an excitatory postsynaptic potential (EPSP)
  
  • The permiability for Na⁺ at the postsynaptic membrane is increased (depolarization-yes action potential)
• When a synaptic connection between two neurons is “inhibiting,” such that there are no action potentials passed from neuron 1 to neuron 2, it is known as an inhibitory postsynaptic potential (IPSP)
  
  • The permiability for K⁺ and Cl^- at the postsynaptic membrane is increased (hyperpolarization-no action potential)

Question 10

Excitatory and Inhibitory Together

Answer 10

• If you integrate the action potentials that a neuron receives from both an EPSP and an IPSP connection, it will result in an overall decrease in action potential transfer from pre-neurons to post-neurons

Question 11

What Happens to 2 Oncoming Action Potentials?

Answer 11

• When 2 action potentials meet one another head on, they will stop their propagation along the axon

Question 12

Striation

Tendons

Sarcomere and Z-line

A-band

I-band

H-zone

Answer 12

• It is striated, both transversely and longitudinally
  
  • Longitudinal striations are the myofibrils (contains sarcomeres)
• Tendons connect muscle to bone
• Contractile unit is known as the sarcomere and is bound by Z-lines
• A-band refers to the myosin that binds to the actin filaments
• I-band refers to the region of actin filaments uninhabited by myosin; spans from end of one A-band, across a Z-line, to another A-band
• H-zone is the region between the ends of actin filaments; in the middle of the A-band

Question 13

Contraction Cycle

Answer 13

• When muscle is relaxed, ATP is bound to myosin and mysoin is not bound to actin
  
  • ATP reduces myosin’s affinity for actin; myosin is at 45^o with respect to actin
• ATP is hydrolyzed on myosin and the protein undergoes a conformational change, allowing for binding to actin
  
  • This is a high energy yet stable state
  • Ca²⁺ must be present
• Binding of actin to myosin releases the ADP and P, and induces another conformational change in myosin, shifting it back 45^o
  
  • This is known as the power stroke and pulls the Z-lines together
• Myosin remains bound to actin in the rigor state until ATP binds to myosin, decreasing its affinity for actin

Question 14

Tropomyosin

Troponin

Calcium

Answer 14

• Tropomyosin lines the actin grooves and prevents the binding of myosin to actin
• Troponin is bound to tropomyosin and binds Ca²⁺​
• When troponin binds Ca²⁺, tropomyosin is bumped out of the groove, allowing for myosin to bind to actin
  
  • Relaxed state when no Ca²⁺

Question 15

Sarcoplasmic Reticulum

Transverse Tubule

Answer 15

• The sarcoplasmic reticulum (think endoplasmic reticulum) surrounds the myofibrils, and sequesters the Ca²⁺
• Transverse tubules (T-tubules) run along the Z-lines, and conduct the action potentials from the last synaptic junction
• T-tubules stimualte the release of Ca²⁺ from sarcoplasmic reticulum, allowing for contraction
• Because the way T-tubules are situated on Z-lines, sarcomeres contract simultaneously

Question 16

CNS and PNS

Answer 16

• CNS refers to the central nervous system
  
  • Contains the brain and the spinal cord
• PNS refers to the peripheral nervous system
  
  • Contains all other nerves

Question 17

Afferent and Efferent Nerves

Answer 17

• Afferent__ nerves are sensory nerves, and therefore carry information into the spinal cord and brain
• Efferent nerves are motor nerves, and therefore carry information away from the spinal cord and brain

Question 18

Grey and White Matter

The Cerebral Cortex

Answer 18

• Grey matter refers to the nerve cell bodies and their dendrites on the outermost layer of the cerebrum, the cerebral cortex
• White matter refers to the myelinated axons beneath the grey matter
• IN THE SPINAL CORD, THIS IS REVERSED
  
  • White matter on the outside
  • Grey matter on the inside
• Cerebral cortex has the central suculus, a groove that seperates the motor and sensory corticies

Question 19

Thalamus

Answer 19

• Relay station for much of the visual and auditory information that we recive from our enviornment

Question 20

Hypothalamus

Answer 20

• Concerned with visceral activities of the body

Question 21

Pituitary Gland

Answer 21

• Master enodcrine gland
• Receives information from the hypothalamus and sends out information to regulate differnt parts of the body

Question 22

The Brainstem and Its Function

Answer 22

• The brainstem contains anatomical features like the midbrain, cerebellum, pons, medulla, and the reticular formation
• These areas coordinate motor and visceral activites; detects movement
• Senses pleasure and pain
• Cerebellum is responsible for the bulk of muscular activity

Question 23

Reflex Arc

Answer 23

• A neural pathway that controls an action reflex
  
  • Patellar tendon is hit with hammer
  • Affernt neurons carry message to spinal cord
  • Sensory nerves stimulate effernt nerves
  • Effernt nerves will induce contraction of quadricepts and biceps (extensor and flexor, respectively)

Question 24

Autonomic Nervous System

Answer 24

• Part of the effernt division of the PNS
• Can be divided in sympathetic and parasympathetic
• Nerve fibers from the autonomic nervous sytem have the spinal cord to innervate various glands, smooth muscle, and cardiac muscle

Question 25

Parasympathetic Division

Answer 25

• Parasympathetic nerve impulses tend to increase the rate of digestion and lower the heart rate
• From sarcal (bottom) region of spinal cord and midbrain/medulla
• The blood pressure is also lowered, and the pupil constricts
• Conserves energy, digestion, rest
• Pre- and postganglionic nerve fibers release ACh

Question 26

Sympathetic Divison

Answer 26

• Sympathetic divison nerve fibers tend to conditino the body for a “fight or flight” response
• Branch off from the thoraic and lumbar (middle) regions of the spinal cord
• Preganglionic nerves, collectively known as the sympathetic trunk can enter the synapse with many other ganglia
• Preganglionic nerves use ACh and postganglionic nerves release norepinephrine are known as adrenergic
• When adrenal medulla (on top of kidney), norepinephrine and epinephrine are released into blood
  
  • Norepinephrine and epinephrine are hormones because they are released directly into the blood

Question 27

Somatic Vs. Autonomic Nervous System

Answer 27

• Somatic nerves innervate close to the effector organ
  
  • ACh is released
  • Innervates skeletal muscle; leads to excitation of the muscle itself
• Autonomic nerves synapse with a ganglion before they make the final synapse with their effector organ
  
  • Preganglionic nerves of para- and sympathetic nervous systems release ACh
  • Postganglionic nerves of sympathetic nervous system releases norepinephrine
  • Innervates glands and smooth & cardiac muscle; can be either excitatory or inhibitory