Chen Quiz Study Set

Neurovascular unit

functional unit composed of interneurons, endothelial cells, microglia, pericytes, astrocytes. Responsible for blood supply, and capable of regulating local blood flow

Choroid plexus

where CSF is produced in brain. Is formed by invagination of ependymal cells into the ventricles, which become richly vascularized

Interstitial fluid (ISF)

extracellular fluid, fluid that circulates in brain, has a specefic concentration of K+ , A lot of things produce ISF

Tight junction

belt like region of adhesion between cells. regulates paracellular flux

Meninges

three protective layers surrounding the brain:

1) Dura mater

2) Arachnoid

3) Pia mater

Dura mater

outer layer, two fibrous layers. Space between 2 layers includes tissue fluids, blood vessels, and lympathic system

Arachnoid

CSF found under this layer, arachnoid membrane= epitehlial layer. Does not allow brain’s underlying folds

Pia mater

innermost layer, follows brain’s underlying folds. Accompanies the branches of cerebral blood vessels

Receptor-mediated transcytosis

required specific binding of ligand to membrane receptor followed by endocytosis

Adsorptive-mediated transcytosis

involved nonspecific binding of ligand to membrane surface receptor, followed by endocytosis

Perivascular endfeet

specialized foot processes of perivascular astrocytes that are closely opposed to the outer surface of brain micro vessels, also have functions in regulating BBB

Pericyte

a cell of mesodermal origin, and contractile-phagocytic phenotype associated with the other surface of capillaries

Basal lamina

the extracellular matrix layer produced by the basal cell membrane, used as an anchoring and signaling site for cell-cell interactions

3 things that protect the brain

bones of cranium, cranial meninges, CSF fluid

Arteries

internal carotid arteries and vertebral arteries. Deliver blood to body organs

Veins

internal jugular veins, carry deoxygenated blood from organs back to the heart to become oxygenated

Blood Brain Barrier

composed of capillary endothelial cells (tight junctions), basal lamina, end feet of astrocytes, pericytes. Functions include having high selective permeability, limited paraceullar solute flux, and they regulate the composition and volume of brain’s ISF

Brain ISF vs. Blood

• ISF has lower pH

• ISF has lower ptoein content, and a lowered buffering capacity

• low glucose conc

• low k+

• low HCO3-

CSF

around the brain and spinal cord, provides cushion and protection, maintains chemical stability, and helps clean waste. Tofu analogy

Amygdala

part of limbic system, involved in emotional reactions. Anger and fear, feeding, sexual interest, fight/flight response

Broca’s area

small region in left frontal lobe that is linked to speech production

Central sulcus

primary groove in brain’s cerebrum, separated frontal lobe in front from occipital and partial lobes in the back of the brain

Cerebellum

located at top of brainstem, coordinated brain’s instructions for skilled, repetitive movements, and helps maintain balance and posture

Cerebrum

largest brain structure in humans, 2/3 of brain mass. Is divided into left and right hemispheres, has all lobes along with their functions

Corpus callosum

collection of nerve fibers connecting the two cerebral hemispheres

Hippocampus

critical for memory and learning, converts STM to LTM

Hemisphere

refers to left and right half of brain, separated by deep groove

Limbic system

plays complex role in emotions, instinct, and appetitive behaviors

Midbrain

aka mesencephalon, a small part of the brainstem that plays an important role in movement along with auditory/visual processing

Motor cortex

part of brain’s cerebrum, involved in movement and muscle coordination

Prefrontal cortex

part of cerebrum in forward part of frontal lobe, involved in planning, reasoning, and social cognition

Premotor cortex

area of cerebrum located between prefrontal and the motor cortex in frontal lobe. Involved in planning and execution of movements

Suculus

a shallower groove on brain’s cerebrum (deeper grooves=fissures)

Visual cortex

area of cerebrum specialized for vision. Lies in occipital lobe at the rear of the brain, is connected to eyes by optic nerves

Wernicke’s area

left temporal lobe, involved in comprehension of speech

Cerebrum

has higher brain functions

Diencephalon

centers for homeostasis

Brainstem

autonomic centers and reflex centers

Cerebellum

involved in coordination and movement and much more

Frontal lobe

motor, speech, memory formation, personality, emotion

Parietal lobe

somatosensory cortex, sensation

Occipital lobe

visual processing and storing visual memories

Temporal lobe

hearing, speech, language, smell, memory retrieval

Insula

considered the 5th lobe, located deep to the temporal lobe

Ventromedial prefrontal cortex

inhibiting inappropriate behavior

Orbitofrontal cortex

cognitive processing of decision-making

Excitability

outside stimuli can initiate electrical charges in muscle resulting in the muscle fiber (muscle cell) contracting

Contractility

stimulation of muscle fiber, causing it to shorten

Elasticity

muscle fiber’s ability to return to its orginal shape after expreincing tension/contraction

Extensionability

ability to be stretched beyond relaxed length

Motor unit

a single motor neuron and all the muscle cells it activates/innervates. Motor unit can usually only control a few muscle cells, larger muscles tend to have more motor units

Henneman’s Size principle

as force increases in a muscle, more and larger motor units are recruited to generate larger force

Muscle fiber

a muscle cell

Muscle fassicle

a bundle of muscle fibers/muscle cells

Muscle tone

continued stready, low level of contraction that stabilizes joints and maintains general muscle health

3 types of motor neurons

1) S type: small, highly excitable

2) FR type: are big, average excitable

3) FF type: very big, low excitable

Sarcolema

plasma membrane in muscle cell

Sarcoplasmic reticulum

SR , is the endoplasmic reticulum in muscle cells

Myofibrils

are cylindrical, have protein based fibrous structures, and extend the entire length of the cell. (can shorten, resulting in contraction, producing motion

Sarcomere

the functional contractile unit in skeletal muscle fiber. Myofibrils contain multiple and repeating sarcomeres

Myofilaments

short bundles that make up the myofibrils. There are 2 types of myofilaments (thin filaments = actin) and (thick filaments = myosin)

Actin

thin filaments, has double helical structure as molecules are twisted around each other. Two primary regulatory proteins are tropomyosin and troponin C.

G-actin

globular actin monomers, individual actin molecules

F-actin

filamentous actin polymers, strands of actin molecules

Myosin

thick filaments, have thick globular heads and long filamentous tails

Sliding filament theory (model)

thin filaments slide across thick filaments towards the center of the sarcomere, resulting in shortening of H and I zone. Z-lines move closer together, A-band does not change

H-zone

spans only partial area of thick filaments

I-band

spans only the thin filaments

A-band

spans entirety of thick filaments

M-line

the line in the middle

Z-line

lines at each end

Rigor mortis

stiffening of muscles when a person dies

Molecular basis of muscle contraction

1) Ca2+ increases in the cytoplasm

2) Ca2+ molecule binds to troponin (TN)

3) Tropnonin- Ca2+ complex pulls tropomyosin strings away from the actin/myosin binding site

4) Myosin head binds to actin, completing the power stroke

5) Actin filament moves

Power stroke

occurs when phosphate is released, triggering power stroke to move actin filaments. ADP disassociated, ATP binds, making myosin detach from the actin

Components of NMJ

1) Synaptic knob: the extended part of the neuron

2) Synaptic vesicles: membrane bound sacs that are filled with acetylcholine (ACh)

3) Synaptic cleft: narrow space separating the synaptic knob from the motor end plate

4) Motor end plate: basically area in synaptic cleft, folds and indentations help to increase SA

5) ACh receptors: receptors in motor end plate that allows ACh to have a binding site

6) Acetylcholinesterase (AChE): an enzyme in synaptic cleft that rapidly breaks down ACh.

T-tubules

deep invaginations of sarcolema, extend into sarcoplasm (also the thing that action potential travels down)

Terminal cisterane

Ca2+ sacs at the end of the sarcoplasmic reticulum

Excitation contraction coupling process

1) somatic neuron releases ACh into NMJ

2) ACh binds to NACHr receptors, opening them, allowing a net entry of Na+ into the muscle cell, initiating a muscle AP

3) AP in muscle cell travels down t-tubule altering the conformation of DHP receptor

4) DHP opens RYR, allowing Ca2+ to leave the SR and enter the sarcoplasm, resulting in contraction

5) Ca2+ binds to troponin, allowing actin-myosin crossbridging

6) Myosin heads execute power stroke

7) Actin filaments slide towards center of sarcomere

DHP receptor

a voltage sensitive receptor that moves in response to AP. Has plug that pulls out of RYR receptor

RYR receptor

a mechanical gated channel that opens in response to plug being pulled out of it

Troponin

calcium sensor in skeletal and cardiac muscle

Cardiac myocytes

cardiac muscle fibers, heart muscle cells. These muscle cells are found in heart wall, are striated, have 1 or 2 nuclei, feature y-shaped branching

Intercalated discs

help spread single with the assistance of gap junctions. How cardiac myocytes are joined to one another, have gap junctions AND desmosomes

Cardiac action potential

is longest action potential compared to the skeletal and smooth APs. Has a Ca2+ plateau that lasts around 200 m/s

Autorhythmic pacemaker cells

sets pace for heart rate, are located in SA node of heart

Sympathatic nervous system

norepinephrine (NE), fight or flight, upregulate

Parasympathetic nervous system

acetylcholine (ACh), rest and digest, down regulate

L-type calcium channels

channels exclusive to cardiac muscle cells. are voltage gated channels that allows Ca2+ to FLOW IN to the cardiac cell

SERCA pumps

an active transporter, ATPase (utilizes ATP) that pumps Ca2+ against its concentration gradient from sarcoplasm back into the sarcoplasmic reticulum

How is cardiac muscle different than skeletal muscle

Cardiac muscle has:

• shorter fibers

• have branches and gap junctions

• can be uni or binucleated

• Ca2+ plateau

• Is involuntary

Smooth muscle properties

found in gut and blood vessels. Pear like shape (short fusiform cells). Long centrally located nucleus. NO STRIATIONS as it is “smooth”. Has less SR. Thin actin filaments are attached to DENSE BODIES (not z-lines). Under involuntary control and still are excitable. No sarcomeres as they are smooth, have longer actin

Attachment plaques

structure present in smooth muscle that resembles adhering junctions. Purpose is to hold cells together.

Smooth muscle physiological properties

have altered myosin-actin arrangement. (filaments are loosely arranged allowing for flexibility). Longer actin filaments along with myosin push ANTI-PARALLEL. Myosin ATP-ase activity is much slower, myosin light chain kinase (MLCK) plays a regulatory role, and there is a diff. Ca2+ mechanism

Kinases

add phosphate, phosphorylation, activate a protein

Phosphatase

remove phosphate, dephosphorylate, deactivate protein

What does Ca2+ bind to in smooth muscle

In smooth muscle, once Ca2+ enters the cell, it binds to RYR receptors, initiating calcium release form SR to sarcoplasm. This is an example of a ligand mechanism, and positive feedback system. This is also true for cardiac muscle cells

Smooth muscle contraction procedure

1) Ca2+ conc. inside cell increases as Ca2+ enters cell and Ca2+ leaves SR

2) Ca2+ binds to calmodulin

3) Ca2+ and calmodulin complex activate MLCK

4) MLCK phosphorylates (adds p group) to myosin heads and increases myosin ATPase activity

5) Active myosin cross bridges slide on actin and create tension/contraction

IP3 receptor

receptor present on surface of sarcoplasmic reticulum, is an example of a ligand gated ionotropic receptor. is activated when IP3 binds to receptors releasing Ca2+

Smooth muscle relaxation steps

1) free ca2+ in cytosol is decreases when ca2+ is pumped out via serca pump

2) Ca2+ unbinds from calmodulin

3) Myosin phosphatase removes phosphate from myosin, which decreases myosin ATPase activity

4) Less myosin ATPase results in decreased muscle tension/contraction

Muscle tension

force created by muscle