Test 2 Review

Endocrine System

100

Difference between alpha and beta cells

–Alpha (α) cells - –Constitute about 17% of pancreatic islet cells

–Secrete glucagon

–Beta (β) cells - Constitute about 70% of pancreatic islet cells

–Secrete insulin

200

What is it called when there are elevated levels of glucose in the blood? What cells does this stimulate?

Purpose of insulin?  

Hyperglycemia

Beta cells - secretes insulin

uptake glucose into the cell

300

Low levels of blood glucose is called? 

What does this stimulate? 

Hypoglycemia

alpha cells - glucagon - break down glucose (glycogenolysis)

400

Difference between water soluble and lipid soluble hormones

–Lipid soluble: Carried in blood via transport proteins

–Lipid soluble hormones such as steroids and thyroid hormones can easily pass through the lipid rich plasma membrane.

–Steroid hormones; Thyroid hormones

–Water soluble: Circulate alone/free in blood; Lipid insoluble hormones such as peptide hormones cannot pass through the plasma membrane and enter the target cell.

–Can only interact with the surface of the target cell

–These hormones binds to membrane receptors on the outer surface of the target cell's plasma membrane.

–Amine hormones; Peptide/protein based hormones

500

Discuss insulin-function uptake of glucose

1.Insulin binds to an insulin receptor in the plasma membrane of its target cell

2.Activates tyrosine kinase, causing them to phosphorylate each other at tyrosine amino acids

3.Sites serve as docking sites where insulin-receptor substrates (IRSs)can bind

4.Once phosphorylated, IRS are activated and trigger intracellular pathways

5.Causes insertion of glucose transporters (GLUTs); the isoform that is insulin-dependent is GLUT4

6.GLUT4 molecules enhances diffusion of glucose into the cell

Nervous Tissue

100

Discuss differences in afferent and efferent nerve endings

Afferent - electrical away from the Muscle

Efferent - signals FROM the CNS to SKM

200

Discuss the differences between PNS AND ANS

PNS-nervous tissue outside the Central Nervous System (CNS) and is divided into afferent and efferent divisions

ANS - conveys output from the CNS to smooth muscle, cardiac muscle, and glands, and is considered involuntary

300

What is the membrane potential based on? 

*hint, how does it operate?

–Voltage: electrical potential difference between opposite charges

–Voltage that exists across the plasma membrane

–Accumulation of positive and negative charges right along the membrane

–Resistance: hindrance of flow of charges

400

Discuss depolarizing, repolarizing, and after-hyper polarizing phase

Depolarizing -

–Negative membrane potential becomes less negative, reaches zero, then becomes positive

–The rising of phase of the action potential. –Occurs until the membrane potential goes up to +30mV

–Na+ channel activation gates open

Repolarizing- 

–The falling of phase of the action potential. This occurs until the membrane potential gets back to rest –70mV; –Na+  channel gates close and K+ open

Hyperpolarizing - 

–After resting membrane potential is re-established, the membrane potential becomes even more negative; Typically goes down to –90mV; –K+ continues outflow, building up more negative charge

500

List all the components of the Neuron and functions 

Cell Body - –Contains organelles; control center for neuron; –Cluster of cell bodies in the PNS is called ganglion; cluster in CNS is called nucleus

Dendrite - receives signals from other neurons

Tips of axon terminals swell into Synaptic end bulbs 

axon - –Functions as the output portion of the neuron by generating action potentials and then propagating them toward another neuron, muscle fiber, or gland cell

Within synaptic end bulbs are synaptic vesicle - stores NTs

Myelin Sheath - increases speed of conductin of APs

Nervous Tissue 2

100

What is typical resting membrane potential? How do we overcome this ? 

-55 mV

through a graded potential past the threshold from neurotransmitters or sensory neurons; considered passive since it comes from the neuron’s membrane

200

Functions of Nervous Sytem (3)

–Sensory : –Sensory receptors detect external or internal stimuli, and relay sensory information to the brain and spinal cord for integration. 

–Integration : CNS analyzes sensory information, and makes decisions for appropriate responses.

–Motor: Motor information is conveyed from the CNS through cranial and spinal nerves of the PNS to appropriate effectors (muscles and glands).

300

Difference between graded potential and action potential? 

Graded - occurs along dendrtites, mechanical or chemical-  come from neurotransmitters or sensory neurons; considered passive since it comes from the neuron’s membrane

Action potential - occur due to the active membrane depolarization reaching a threshold to fire, caused by a shift of ions; occur along axons, voltage gated

400

Discuss different types of channels 

Ligand - –Participate in the generation of graded potentials

Leak channels - establishes resting membrane potential

 Mechanically gated - –Involved in the formation of graded potentials (touch, pressure, tissue, stretching)

Voltage - –Responsible for the generation and conduction of action potentials

500

Discuss signal transmission at a chemical synapse

1.An action potential arrives at a synaptic end bulb of a presynaptic axon

2.The membrane of the synaptic end bulb contains voltage-gated Ca+2channels in addition to the Na+ and K+ channels 

–depolarization phase of AP opens not only Na+ but Ca+2 as well

3.An increase in Ca+2 triggers exocytosis of the synaptic vesicles

–This results in fusion of the synaptic vesicle with the presynaptic membrane, releasing neurotransmitter molecules into the synaptic cleft

–Example: acetylcholine

4.Neurotransmitter molecules diffuse across the synaptic cleft and bind to neurotransmitter receptors on ligand-gated channels

5.This binding opens the channels and allow ions to flow across the membrane 

6.As ions flow, voltage changes (postsynaptic potential)

–may be depolarization or hyperpolarization based on which ion channels open

7.When a depolarizing postsynaptic potential reaches threshold, it triggers an action potential in the axon

Muscle

100

During muscle contraction, what protein does calcium bind to? 

Troponin C of Actin protein

200

Discuss the properties of myosin AND actin 

2 globular heads

Myosin heavy chain (MHC) is the motor protein of muscle thick filament

2 chains per myosin head

contains an ATP binding site and actin binding site

ACTIN:

–Thin, Double stranded binding site for myosin

–Individual actin molecule: G actin

–G actin links together: F actin

300

Discuss regulatory and structural proteins 

What protein is responsbile to stabilize the sarcomere during eccentric contractions? 

TITIN

–Tropomyosin

–Covers the active sites on actin, preventing myosin from binding to actin when fiber is at rest

–Troponin

–Binds with Ca+2, changes shape, causes tropomyosin to move off active site, allowing myosin to bind to actin

–Titin, Alpha-actinin, Myomesin, Nebulin, Dystrophin 

–Elastic proteins

–Contribute to the alignment, stability, extensibility, and elasticity of sarcomere

400

Discuss the structure/ components of the Skeletal muscle fiber

& organization

–Sarcolemma: plasma membrane of muscle fiber

–Surrounds muscle fiber and regulates entry and exit of materials

–Sarcoplasm: cytoplasm of muscle fiber - –Site of metabolic processes for normal muscle fiber activities

–Sarcoplasmic reticulum: smooth endoplasmic reticulum in muscle fiber - –Stores Ca+2 needed for muscle contraction

–Terminal cisternae: expanded ends of the sarcoplasmic reticulum that are in contact with the transverse tubules (2 + T-tubule = triad)- –Site of Ca+2 release

–Transverse tubule (T-tubule): extension of the sarcolemma into the sarcoplasm, wrapped around myofibrils - Quickly transport a muscle impulse from the sarcolemma throughout the entire muscle fiber

–Muscle - Covered by Epimysium - –Bundle of fascicles

––Fascicles- –Covered by Perimysium - Bundle of Muscle Fibers

––Muscle Fibers (muscle cell)*- Covered by Endomysium - Contains myofibrils

–Myofibrils - –Contractile element - Composed of myofilaments

–Myofilaments* Contractile proteins

–Thick- myosin & Thin- actin, tropomyosin, and troponin

500

Discuss Excitation contraction coupling 

1.A nerve AP in a somatic motor neuron travels to the NMJ and triggers the release of ACh

2.ACh binds to receptors in the motor end plate potential causing depolarization of the sarcolemma (EPP) by opening ion channels and allowing Na+ in and K+out of the muscle cell

–Acetylcholinesterase destroys ACh so another AP does not arise unless more ACh is released

3.Depolarization creates a wave of AP  across the sarcolemma and down the T-tubule

4.This triggers dihydropyridine receptors (DHP)  to open Ca+2 release channels (ryanodine receptors)

5.Ca+2 is released from the terminal cisternae of the sarcoplasmic reticulum (SR) into the sarcoplasm

6.Ca+2 binds with troponin, which removes the blocking action of Tropomyosin from the actin binding sites

7.ATP binds to myosin, and is hydrolyzed, giving myosin energy

8.Myosin attaches to actin and forms a cross bridge

9.Myosin cross bridge pivots, pulling the thin filament past the thick filament toward center of sarcomere

10.ATP attaches to myosin, detaching from actin; contraction continues until AP stops and Ca+2  is returned (sequestered) to the SR