Human Skin and Muscle Anatomy & Physiology: Key Concepts for Biology

Which of the following is a layer of the true skin?

The epidermis

The most superficial layer of the epidermis is made up of

Many layers of dead keratinocytes

Which of the following are sensory receptors in the skin?

Pacinian corpuscle, Meisner's corpuscle, and Hair follicle receptor

Water loss through our skin on a very cold, windy day is mostly

Insensible perspiration

Which of the following is a receptor that is activated in a feedback loop that responds to increased body temperature?

Thermoreceptor

Sebaceous glands normally secrete contents

Onto the skin surface through hair follicles

In order for melanin to protect against at least two types of skin cancer, the pigment must be passed to

Epithelial cells

Water loss from a third degree burn would be classified as

Insensible perspiration

In the negative feedback loop that restores body temperature when we get hot, the effector consists of

Sweat glands

The types of cell that gives rise to a basal cell carcinoma is in the

Stranum bassale

What is the most likely result from the increased sebaceous activity during puberty?

Increased oily appearance and more acne

Which of the following is an effector that is activated in a feedback loop that responds to increased body temperature?

Sweat gland

Why might a humid day with a temperature of 70F feel hotter than a dry day with a temperature of 80F?

Sweat doesn't evaporate. If sweat doesn't evaporate, it can't cool a person.

When a person becomes hot, they become

Redder

Which of the following prevents most insensible perspiration?

The epidermis

In high humidity, what happens to the feedback loop that helps maintain body temperature?

Everything works normally, but the environment diminishes the effectiveness of the feedback loop.

If a burn is very painful, it is likely third degree (full thickness). True or False?

False

Which of the following affect skin color?

Blood flow and the amount of melanin

How many layers does the dermis have?

Two layers

What is the deepest layer of the epidermis?

Starnum basale

What is responsible for goose bumps?

Arrector pili muscle

What is the function of melanin?

Protect cell nuclei from damaging UV radiation

What causes a suntan?

Increased UV radiation activating melanocytes, resulting in a darkening of the skin

The type of cell that gives rise to a squamous cell carcinoma is in the

In the epidermis, but in neither the stratum corneum nor stratum basale

Why does someone suffering a heart attack turn blue?

Blood becomes deoxygenated and deoxygenated blood look blue through skin

The epithelial tissue of the skin is particularly well suited to its function because

Multiple layers of cells protect against entry of harmful substances and loss of vital substances

As demonstrated in the skin, blood vessels travel through what tissue type?

Connective

Fluid replacement is critical for individuals suffering extensive 3rd degree burns. This is because

Insensible perspiration is dramatically increased

If melanocytes were so active that all cells in the body contained enormous levels of melanin, the individual would appear

Dark brown or black

What is a synergist muscle?

A muscle that assists the prime mover for a motion

What action would a muscle originating on the coracoid process and inserting on the radial tuberosity perform?

Flex the shoulder and flex the elbow

If the deltoid contracted moving the hand at 1 meter per second, how would the insertion move?

Slower than one meter per second

What does a motor unit refer to?

All fibers stimulated by a specific motor neuron

What is the threshold voltage in a muscle fiber?

The voltage at which voltage-gated sodium channels open

What causes relaxation in a skeletal muscle fiber?

Calcium is pumped away from myofibrils

What is a motor neuron and the muscle fibers it innervates called?

Motor Unit

Why is muscle considered a motor?

Converts chemical energy to mechanical energy

If only sodium channels were open, what would the membrane potential be?

About +66 mV

What would the membrane potential be in a muscle fiber treated for a long time with succinylcholine?

Above threshold

What happens when a muscle contracts?

Z-line move closer together

In order to extend the elbow, what must happen?

Antagonists to elbow flexion must contract

As a muscle exerts more force, what is always true?

More cross bridges form

What is the state of a muscle fiber treated for a long time with succinylcholine?

Relaxed

What occurs when acetylcholine binds its receptor at the motor end plate?

A graded depolarization occurs

What happens to a muscle fiber that fires a single action potential but never repolarizes?

Generate force until ATP is depleted

What happens if the immune system destroys all ACh receptors on a skeletal muscle fiber?

Membrane potential would remain negative, voltage-gated sodium channels would be closed, and the muscle fiber would not generate force.

What is a group of muscle fibers surrounded by perimysium called?

Muscle fascicle

When does a muscle fiber generate the most force?

During an isometric contraction

Why does smooth muscle appear smooth?

Smooth muscle cells do not have sarcomeres

Where are motor proteins located in a muscle fiber?

Thick filaments

What is the tissue that surrounds a muscle fascicle called?

Perimysium

What is the tissue that surrounds an individual muscle fiber called?

Endomysium

When do voltage-gated sodium channels open?

The membrane potential reaches a threshold voltage

Where are the primary motor proteins in muscle found?

Thick filaments

When the pectoralis major contracts while throwing a ball, how does the hand move relative to the insertion?

Faster than the insertion of the muscle

In a third-class lever system during a ball throw, how does the distal part of the arm move?

The distal part of the arm moves faster than the insertion of the brachialis

What would a muscle originating on the ischial tuberosity and inserting on the head of the fibula do?

Flex the knee and extend the hip

If a muscle fiber voltage is held at -70 mV, what ion injection would cause contraction?

Calcium

Which proteins are components of the thin filament?

Tropomyosin, Actin, and Troponin

What happens to a muscle fiber that fires repeated action potentials at a rapid rate?

Generate force until ATP is depleted

In skeletal muscle, an action potential is most directly caused by the opening of what?

Voltage gated sodium channels

Why does skeletal muscle relax?

Calcium pumps are always removing calcium from the SR (sarcoplasmic reticulum)

In skeletal muscle, what protein binds calcium to initiate contraction?

Troponin

How do the triceps surae (gastrocnemius and soleus) act on the ankle?

Second class lever

What is the result if tubocurarine binds to the nicotinic ACh receptor and locks it in a closed position?

No action potentials would be fired

If a person has been dead for a day, how does the calcium concentration in the fluid surrounding the myofibrils compare to the sarcoplasmic reticulum?

Equal to the calcium concentration in the sarcoplasmic reticulum

How are tendons connected to bone?

Collagen fibers from connective tissue in the muscle interweaving with collagen fibers from the periosteum and bone tissue

Skeletal muscle fibers generate maximal force when they are at what length?

Intermediate length

How many nuclei does a neuron have?

One

What do afferent neurons carry?

Sensory signals

What would happen if the release of acetylcholine at the neuromuscular junction were blocked?

Flaccid paralysis

In the nervous system, where does most information processing occur?

CNS (Central Nervous System)

Which ion channels predominate in the dendrites of neurons?

Ligand-gated channels

What are the effector tissues in the autonomic nervous system?

Glands and smooth muscle

What is the effector tissue in the somatic nervous system?

Skeletal muscle

What structures are included in the central nervous system?

The brain and the spinal cord

Why is the disruption of myelination in multiple sclerosis a problem?

Action potentials from non-myelinated neurons are not timed correctly

What is the function of myelin?

Insulates axons and causes action potentials to travel faster

Which cells myelinate axons in the central nervous system?

Oligodendrocytes

If a neuron's membrane potential is -60 mV and chloride channels open (equilibrium potential -65 mV), where does chloride travel?

Into the cell

If only sodium channels were open, what would the membrane potential be (equilibrium potential +66 mV)?

About +66 mV

Which nervous system branch increases heart rate when frightened?

Sympathetic

Which cells control the activity of smooth muscle in the gut?

Autonomic motor neurons

Which cells maintain the blood-brain barrier?

Astrocytes

What predominates in a neuron's dendrites?

Graded potentials

Which of the following would relax a neuron?

Graded hyperpolarization or chloride moving into the cell

Which fibers transmit signals the fastest?

Myelinated large diameter fibers

If potassium channels remained open and all other ion channels were closed, what would the voltage inside a neuron be (equilibrium potential -90 mV)?

-90 mV

What cells myelinate axons in the central nervous system?

Oligodendrocytes

Lidocaine would block sensory signals while allowing muscle contraction if it did what?

It blocked voltage gated sodium channels in sensory neurons

What is the effector tissue in the autonomic nervous system?

Glands and Smooth muscle

If we shock an axon in the middle, bringing the voltage inside above threshold, what happens?

An action potential will be generated and will travel in both directions

If we blocked the release of acetylcholine at the neuromuscular junction, what would a person experience?

Flaccid paralysis

If a neuron's resting membrane potential is -70 mV and there were consistent graded membrane potentials, what would you expect the voltage inside the cell to become?

I need more information

Since glutamate is a major excitatory neurotransmitter, what do most glutamate receptors do?

Depolarize a neuron

During the relative refractory period, what is the state of voltage-gated potassium channels?

Open

During the relative refractory period, what is the state of voltage-gated sodium channels?

Closed

During the absolute refractory period, what is the state of voltage-gated sodium channels?

Inactivated

During the absolute refractory period, can a neuron fire another action potential?

Cannot fire another action potential

Why does an action potential that begins at the axon hillock travel only towards the axon terminal?

After depolarizing, each portion of the axon enters the absolute refractory period so it can't transmit a signal either backwards or forwards.