Anatomy lecture exam 3

What are reflexes?

Involuntary responses to stimuli; can be neural (somatic/autonomic motor) or endocrine (hormones).

What are the components of a reflex arc?

Receptor → Sensory neuron → Integration center → Motor neuron → Effector.

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Where is the sensory neuron soma located?

In the dorsal root ganglion.

monosynaptic

A reflex where the sensory neuron synapses directly with a motor neuron.

What is a polysynaptic reflex?

A reflex that involves an interneuron between the sensory and motor neurons.

What happens to sensory information during a reflex?

Collaterals send the information to the brain while the reflex occurs.

What are the four ways reflexes are categorized?

Time of development (innate vs. acquired)

Processing site (cranial vs. spinal)

Response type (somatic vs. visceral)

Number of synapses (mono- vs. polysynaptic)

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What is the stretch reflex?

A monosynaptic reflex that prevents overstretching of a muscle.

What are intrafusal fibers?

Muscle spindle fibers wrapped with sensory receptors that detect stretch.

What are extrafusal fibers?

The regular skeletal muscle fibers responsible for contraction.

What is the Golgi tendon reflex?

A polysynaptic reflex that prevents tendon tearing by inhibiting the contracting muscle and stimulating its antagonist.

What receptors trigger the Golgi tendon reflex?

Golgi tendon organs located in tendons.

What is the withdrawal reflex?

A polysynaptic reflex that activates flexor muscles to withdraw from a painful stimulus.

Which receptors detect painful stimuli for the withdrawal reflex?

Nociceptors.

What is the crossed extensor reflex?

A reflex that activates contralateral extensors to maintain balance during the withdrawal reflex.

Define ipsilateral.

Occurring on the same side of the body.

Define contralateral.

Occurring on the opposite side of the body.

What is reciprocal inhibition?

Inhibition of antagonistic muscles to allow desired movement without opposition.

What is a reverberating circuit?

A neural circuit that maintains a muscle contraction until it is inhibited.

How can the CNS influence spinal reflexes?

It can facilitate or inhibit them.

What is the Babinski reflex?

Dorsiflexion of the big toe and fanning of other toes when the sole is stroked.

What is a positive Babinski sign?

Presence of the reflex big toe dorsiflexes, toes fan.

What is a negative Babinski sign?

Normal plantar flexion of toes.

Why do children under 4 often show a positive Babinski sign?

Their corticospinal tracts are not fully myelinated yet.

What does a positive Babinski sign in someone older than 4 indicate?

Damage to corticospinal tracts or upper motor neurons.

polysynaptic

more complex, many effectors and synapses

monosynaptic

involving one effector and one synapses

Time of development

innate vs acquired newborn (sucking,grasping)

location of processing site

cranial vs. visceral (smooth muscle, skeletal muscle)

number of synapses

monosynaptic vs. polysynaptic

What happens when light hits retinal?

Cis → trans conversion

After retinal activates opsin, what is the enzyme cascade?

Opsin → transducin → phosphodiesterase

What does phosphodiesterase do?

Breaks down cGMP

What happens when cGMP decreases?

Na+ channels close → membrane hyperpolarizes (–70 mV) → glutamate stops

What is "bleaching"?

Delay while retinal is rebuilt into cis form

Do rods or cones have more convergence on bipolar cells?

Rods

What do M cells detect?

Black/white information (from rods)

What do P cells detect?

Color and detail (from cones)

Where do ganglion cell axons exit the eye?

Optic disc

Which axons cross at the optic chiasm?

Medial axons

What are the sensory receptors for hearing and equilibrium?

Hair cells

What opens mechanically-gated channels in hair cells?

Bending of stereocilia

What structure vibrates first in hearing?

Tympanic membrane

What creates pressure waves in perilymph?

Stapes pushing on the oval window

Where does rotational equilibrium occur?

Semicircular canals (crista ampullaris)

Where does gravitational equilibrium occur?

Vestibule (utricle & saccule, maculae)

What structures help detect gravity in the vestibule?

Otoliths

Epimysium

Dense layer of collagen fivers surrounds the entire muscle

Perimysium

divides muscles into fasciculi

endomysium

surrounds each muscle fiber

cell membrane

sarcolemma

cytoplasm

sarcoplasm

Functional unit

sarcomeres

T tubles

extensions of interstitial fluid that carry actions potentials from endplate to sarcomeres

Terminal Cisternae

releases calcium

A-Band Dark

extends the length of myosin in the center of the sarcomere

M line

stabilization protein in the middle of the A band that hold myosin in place

H-zone

On either side of M-line and actin overlap

I-band light

outer ends of the sarcomere

Z-lines

stabilization proteins on either end of the sarcomere, stabilize actin

Titin

thin protein that attaches myosin to the Z-line to maintain alignment

Twitch

A single power stroke (one stimulation)

sustained contraction

more than one stimulation

latent period

action potential arrives and cat++ is released

Contraction Period (sliding filament theory)

Ca++ binds to troponin, crossbridge formation and tension is developed

relaxation period

Ca++ is pumped back into terminal cisternae tension decreases

Wave summation

Adding up twitches in order to develop tension

Complete tetanus

maximal tension, due to stimulation again at the beginning of the relaxation phase

Incomplete tetanus

submaximal tension, stimulation occurs again at the end of the relaxation phase

Treppe

an increase in twitch size following previous twitches due to Ca++ buildup

Motor units

a group of muscle fibers innervated by a single motor neuron, work together with other motor units to produce tension

Internal tension

within the muscle fiber

External tension

transmitted to the tendon

Motor unit recruitment

activating motor units sequentially to keep movements smooth

If sarcomeres are too stretched

zone of overlap too short, few crossbridges are formed

If sarcomeres are too shortened

short H-zone (not much room for sarcomeres to shorten further

Isotonic- Concentric contraction

tension exceeds resistance

isotonic-Eccentric contraction

resistance exceeds tension

Isometric

Tension and resistance are equal

 

Stored ATP

last 2 seconds

Creatine phosphate

last 15 seconds

Fast twitch

§Few mitochondria, fatigue quickly

Slow twitch

§More mitochondria, resistant to fatigue

Intermediate

§Characteristics between fast and slow twitch

Hypertrophy

§Increase in mitochondria and stored glycogen proliferation of myofliaments

Atrophy

§Decrease in mitochondria and stored glycogen Decrease in myofilaments

actin consists of what strands?

F actin

F actin is made of?

G actin molecules

G actin has binding sites for?

myosin heads

during rest excess ATP is used to make what?

creatine phosphate which then can be used to make phosphorylate ADP

After energy is used muscle fibers must?

make more ATP using glycolysis and the Krebs Cycle

Glycolysis

In the Cytoplasm, anaerobic and yields 2 ATP and 2 pyruvic acid

Krebs cycle

in the mitochondria, aerobic, Yields 2 ATP, CO2 and NADH and FADH2

electron transport chain

yields 32 ATP 17 pyruvic acid

During Glycolysis what happens energy?

less energy is created, and pyruvic acid turns into Latic acids

During recovery what happens to lactic acid?

Converted back into pyruvic acid