A&P Final

Anxiety

the stress response caused by the sympathetic nervous system without the actual stressor occurring at the time. Activates the pathway between the amygdala and the fight or flight centers in the brainstem and the hypothalamus, and the stress response is the exact same even though the stimulus is not real. Purpose is protective. 

Axon

long projection of the cell that can range in length from a few mm to a meter or more. Conducts the action potential through the body.

Brainstem

portion of the brain that primarily controls autonomic functions of the body. Physiological responses that don’t involve conscious activity or changes in behavior generally originate from the brainstem. Increasing/decreasing heart rate, changing blood flow to different organs.

Cerebellum

“tiny brain” involved in timing and sequencing of motor activities.

Cerebrum

along with the cerebral cortex, makes up the major portion of the telencephalon. gets sensory information from the cerebral cortex, interprets the information and then decides what response to make.

Chemoreceptors 

Specialized nerve cells that bind specifically to certain types of chemicals. Binding to the chemical then causes and action potential that travels through the rest of the receptor and ultimately o the brain

Cornea

Clear connective tissue layer that covers the exposed part of the eye. clear because there is no pigmentation or blood vessels. Lots of sensory nerves. Gets oxygen from the surrounding air and also from some circulation within the aqueous humor.

Diencephalon

Part of the brain that contains the thalamus, hypothalamus and epithalamus. Relay center for sensory information coming in from the periphery of the body and it makes sure that the information gets to the right place in the cerebrum and cerebral cortex.

Hypothalamus

Monitors the internal and external environments and makes behavioral changes in response.

Mechanoreceptors

Respond to mechanical stimuli by starting an action potential

Myelinated Nerve Cell

nerve cell that has its axon wrapped in layers of myelin. Insulation, dramatically reduces the ability for sodium to enter the nerve cell membrane such that only gaps in the myelin sheath (nodes) can actually have an action potential. Myelination increases the speed at which an action potential can travel along the axon.

Neron

nerve cell

Neurotransmitter (NT)

molecules released by exocytosis from presynaptic nerve cell axons. May be stimulatory or inhibitory. Stimulatory- bind to and activate ligand gated sodium channels on the postsynaptic cell membrane. Inhibitory- bind to and open ligand gates potassium or chloride channels or prevent sodium channels from opening. Cleared from synapse by specific enzymes or reuptake into presynaptic cell for recycling.

Nocieptors

transmit pain signals to the brain

Olfactory nerve

carries action potential from the olfactory receptors to the brain for interpretation and processing for the sense of smell.

Optic nerve

carries action potentials from the retinas to the occipital lobe of the brain for processing of visual information.

Penna

the outer ear that gathers and funnel sound waves into the ear canal towards the tympanic membrane (eardrum). Usually made of cartilage covered by skin and the large the pennae the better the gathering of sound waves.

Pituitary gland

sits at the base of the hypothalamus. Anterior and posterior pituitary gland. 

Propioceptors

receptors within the specialized organs in tendons and muscles that determine the amount of force being produced and this provide the brain with information about the position of the limbs in relation to the rest of the body. Proprioceptive information can also be used to avoid damage to muscle by causing inhibition of contraction as force rises to the point where damage could occur.

Resting membrane potential

condition in which a cell membrane is polarized with more positive charges on one side that the other. RMP can be measure by using micro-electrodes on each side of the cell membrane and is found to have a value somewhere around -90 mV in large neurons at rest.

Retina

portion of the eye that contains the photoreceptors that called rods and cones.

Soma

call body of a neuron. This is the part that contains the nucleus and which synthesizes neurotransmitters and cellular proteins such as voltage gated sodium channels or many other proteins that keep the cell alive and functioning. Membrane around the soma can have waves of depolarization and repolarization just like the membrane surrounding the axon.

Synapse

connection between nerve cels in a neural circuit. Sometimes these will be electrical synapses in which the pre- and post-synaptic nerves are physically connect by gap junctions and sometimes they will be chemical synapses in which the pre-synaptic nerve releases neurotransmitter molecules onto the post-synaptic nerve cell. Electrical are found in the brain and cardiac muscles. Chemical are found throughout the peripheral nervous system and within the brain, also between motor neurons and skeletal muscle cells.

Telencephalon

Portion of the brain that contains the cerebrum and cerebral cortex.

Thalamus

relay center for sensory information coming from the periphery of the body, and it makes sure that the information gets to the right place in the cerebrum and cerebral cortex.

Acetylcholine ACH

Neurotransmitter used by motor neurons to stimulate skeletal muscle cell action potentials, via creation of the end plate potential. 

Acetylcholinesterase ACHase

Enzyme produced by skeletal muscle cells that resides in the synaptic cleft and which breaks down ACH into acetate and choline.

Actin filament

thin filaments within the sarcomere. Consists of two strands of actin surrounded by a strand of tropomyosin that blocks the myosin binding sites on actin. The actin filament also contains troponin, which both hooks tropomyosin to actin and also binds to calcium

Alpha motor nerve

large nerve fiber that causes an action potential and subsequent contraction in skeletal muscle cells. An alpha motor nerve may branch many times and thus stimulate several muscle cells, but each skeletal muscle cell will only be stimulated to contract by a single alpha motor nerve.

Botox

paralytic agent that acts by preventing exocytosis of ACH from alpha motor nerves

Cobra toxin

paralytic agent with multiple modes of action, depending on the type of snake. All modes of action prevent the normal end-plate potential from occurring at the sarcolemma.

Curare

Paralytic agent that works by binding to the AC receptor on the sarcolemma at the motor end plate and preventing ACH from binding. Thus it is an ACH antagonist.

DHP receptor (dihydropyridine receptor)

DHP is located within the triad, specifically within the sarcolemma of the t-tubule. Upon depolarization of that section of the t-tubule, DHP mechanically activates RyR within the sarcoplasmic reticulum to cause the release of stored calcium.

Isometric contraction

type of contraction of skeletal muscle in which the amount of force produced is equal to the load on the muscle and thus no movement occurs. Involved in posture. 

Isotonic contraction

type of muscle contraction in which the force produced is greater than the load on the muscle and thus movement results. involved in locomotion

Laryngospasm

Contraction of the skeletal muscles around the larynx that normally allow the epiglottis to cover the opening of the trachea during eating or drinking. Laryngospasm is an abnormal amount of contraction, as caused by something like sarin gas, and thus prevents air from entering the trachea for an extended period of time. This is usually the cause of death from nerve gasses like sarin.

Motor units

an alpha motor nerve and all the skeletal muscle fibers attached to it. All muscle fibers within a motor unit will be of the same type.

Myoneural juction

technical name for the synapse located between the alpha motor nerve and the skeletal muscle cell’s sarcolemma. 

Myosin filament

Thick filament within the sarcomere. Each filament has a large globular head that has enzyme activity to break ATP into ADP + Pi. The myosin filament also has two flexible regions, a swivel and a hinge, so that when it binds to actin it can release its bound Pi and swivel from 90 degrees to 45 degrees relative to actin. This creates the power stroke during skeletal muscle contraction.

Myosin head

portion of the myosin filament that binds to actin. The myosin head also binds to ATP in preference to actin and will not bind to both actin and ATP at the same time. Once the myosin head is bound to ATP, however, its enzymatic activity will break the ATP down into ADP + Pi. The presence of Pi adds tension to the region of myosin containing the myosin head, and moves, then holds the head at 90 degrees relative to actin until myosin binds to actin once again.

myosin head ATPase

enzyme within the myosin head that converts ATP to ADP + Pi

RyR receptor (ryanodine receptor)

Protein within the sarcoplasmic reticulum that interacts with DHP upon depolarization of the triad, and ultimately opens to allow calcium efflux from the sarcoplasmic reticulum into the sarcoplasm to cause contraction

Sarolemma

skeletal muscle cell membrane

Sarcoplasmic reticulum

specialized form of endoplasmic reticulum that stores calcium and which contains RyR and SERCA proteins in its membrane. Consists of both terminal cisternae at the ends of longitudinal tubules in the middle.

SERCA

Sarco-endoplasmic reticulum calcium pump that uses ATP to pump calcium back into the sarcoplasmic reticulum after contraction. Thus SERCA is a primary active transporter.

Synaptic troughs

loops of sarcolemma that occur at the motor end plate to create increased surface area and house large numbers of ACH receptors 

Synaptic vesicles

membrane wrapped containers of NT within the terminal region of the alpha motor neurons

T-tubule (transverse tubule)

internal extensions of the sarcolemma into a muscle cell. Contains DHP and is part of the triad that consists of the t-tubule and terminal cisternae of the SR.

Terminal cisternae

ends of the SR that form part of the triad in skeletal muscle

Tetany 

maximum force of contraction that can be generated by skeletal muscles. Requires all motor units to be contracting and the to contract at maximum speed. Tetany cannot be maintained for more than a few seconds before fatigue will set in. 

Tone

activity of skeletal muscles. Increased muscle tone would result from an increased rate of contraction, usually isometrically. This would occur during increased stress adn activation of the sympathetic nervous system.

Treppe

Mechanism of increasing force of contraction through “warming up” of the skeletal muscles. Likely this involves buildup of calcium ions in the cell such that all troponin C binding sites are occupied. Additionally, more blood flow may help to bring increased nutrients for ATP production.

Triad

Consists of the t-tubule and terminal cisternae of the SR. It is at the triad where the action potential causes the release of calcium to initiate muscle contraction.

Trypomysin

Strand of protein that covers the myosin binding sites on the actin filaments. Rotates out of the way when four molecules of calcium bind to troponin C. 

Troponin C

Calcium binding protein that binds four molecules of calcium. Two binding sites are high affinity and two are low affinity; thus the two high affinity binding sites may be bound to calcium even when sarcoplasmic calcium concentrations are low. Therefore, only two more calcium ions are required to rotate tropomyosin and initiate contraction, making the process occur much more quickly.

Type 1 fibers

Muslce fibers that are smaller, better at making ATP in the presence of oxygen and fatigue resistant. Also called red muscle fibers because they contain a large amount of myoglobin, an oxygen carrying protein that is red in color. Prefer fatty acids as fuel for beta-oxidation. Generally found in greater quantities in muscles that are involved in posture, or isometric contractions.

Type 2 fibers

Muscle fibers that are larger, better at making ATP under anaerobic conditions and fatigue prone. Also called white muscle fibers because they contain lower amounts of myoglobin. Prefer glucose as fuel. Generally found in greater quantities in muscles that are involved in locomotion, or isotonic contractions.

VX/Sarin/Tabun nerve gas 

Family of related compounds that inactivate ACHase. Thus ACH cannot be broken down into choline plus acetate within the motor end plate and the contraction persists. Called a tetanizing agent because maximal muscle contraction is quickly achieved and the muscle cannot relax after being stimulated to contract. Result in laryngospasm and suffocation. 

Uses the vagus nerve to stimulate changes

Parasympathetic nervous system

Uses mostly fast spinal nerves to stimulate changes

Sympathetic

Has hormones that can reach any target tissues that make a receptor for the hormones

sympathetic

Sends nerves to the skin to reduce blood flow

sympathetic

Sends nerves to the heart to reduce heart rate

parasympathetic nervous system

Has no direct impacts on blood flow to the brain

parasympathetic

Uses cranial nerve to dilate the pupils

sympathetic

Has metabolic activities which result in decreased fat storage and increased muscle protein synthesis 

sympathetic 

Stimulates insulin secretion by sending a branch of the vagus nerve to the pancreas

parasympathetic

Reduces insulin secretion by sending a spinal nerve to the pancreas

sympathetic

Condition where there are more positive charges outside the cell membrane and fewer positive charges inside the cell membrane

polarized

Condition where positive charges leave the cell to restore the normal resting potential of the cell membrane

repolarized

Condition where positive charges move into the cell to make the inside of the membrane more positive

Depolarized

Type of feedback involved in transmitting the action potential down the length of the nerve cell acon

Positive feedforward

The point of the action potential is to cause the release of neurotransmitters frmo the end of the nerve axon

True

If 500 sodium ions enter the cell during depolarization, how many potassium ions will leave to repolarize the cell?

500

How can a person with low serotonin increase the activity of these nerve pathways?

• Take a drug that prevents or slows reuptake of serotonin by presynaptic nerves

• Increase daylight hours and thus decrease the synthesis of melatonin

Producing increased vigilance to help prepare for threatening situation

Norepinephrine

Producing feelings of good will after having long face-to-face conversation with a good friend

serotonin

Reducing the stress response after anxiety or fear has triggered increased output from the amygdala

GABA

Increasing the heart rate

norepinephrine

Decreasing the heart rate

acetylcholine

stimulating muscle contraction by alpha motor nerves

acetylcholine

Eating a big bowl of chocolate ice cream and feeling “that was good, do that again”

dopamine

Eating several pieces of roasted turkey and feeling like food needs have been met

serotonin

Shutting down muscle contractions

dopamine

Causing hypervigilance in conditions like PTSD

norepinephrine

Events of muscle contraction

1. Action potential in an alpha motor nerve cell

2. secretion of acetylcholine into the synaptic cleft next to the muscle cell membrane

3. binding of acetylcholine to ligang-gated sodium channels on the sarcolemma

4. action potential in the sarcolemma

5. action potential moving down the t-tubule of the skeletal muscle cell

6. opening of calcium channels within the SR

7. calcium binding to troponin C on the actin filament

8. myosin heads binding to actin filaments

9. power strokes and contraction of the skeletal muscle cell

10. pumping of calcium back into the SR to stop the contraction

Sympathetic Nervous System

• Fast response- uses spinal nerves (happens in milliseconds)

• Widespread- uses hormones

  • adrenal gland- adrenaline→ epinephrine and norepinephrine

Cortisol’s role in the sympathetic nervous system

• increase breakdown of stored glycogen (increase blood glucose)

• decrease inflammation

• decrease immune response (uses energy)

• Increase blood to brain and skeletal muscle

Epi/norepi’s role in the sympathetic nervous system

binds to receptors on their target tissue. B-receptors impact metabolic activity.

Parasympathetic nervous system

• less need to be fast

• less need to be widespread

• save energy - increase digestion, nutrient storage, and insulin

• Uses the vagus nerve 

• A lot of parasympathetic function is directly due to brain stem

Tissue damage

starts nerve impulse (action potential) transmitted along nerve axons and from nerve to nerve

Goal of action potential

reach nerve ending and cause release of a neurotransmitter

How are cell membranes polarized?

outside cell has a high concentration of Na+

inside cell has a high concentration of K+ and - proteins

more positive outside

Facilitated diffusion

Na+ channel- resting cell = closed, opens upon stimulus

stimulus applied, Na+ channel opens, Na+ flows into cell, cell membrane depolarizes

Depolarize

We need enough stimulus to reach threshold potential to initiate this positive feedforward.

Stimulus opens channels and allows a lot of Na+ in. Opens more channels and lets more Na+ in. Positive feedforward

Repolarize

Now we can have another action potential (abundance of Na+ outside)

1. Polarized- Na+ wants in

2. Depolarize- let some Na+ in

3. Repolarize- let some K+ out

After action potential

Na/K active transporter- 3 Na out, 2 K in. Restores the membrane potential and concentration gradient.

Lymphatic system

Provides alternate method for fluid in interstitial spaces to return blood

• Can also carry substances that are too large to re-enter the capillaries

Lymphatic capillaries

• formed by epithelial cells with loose junctions

• overlap to form a kind of valve

  • only lets fluid flow in one direction

  • movement between cells=pericellular

Four types of defense barriers (innate immunity)

• Anatomic

• Physiologic

• Endocytic and phagocytic

• Inflammatory