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There are _______ chemically and voltage gated channels on the sarcolemma.

Many

1

This reversal is due to changes in membrane permeability

At RMP the membrane is more permeable to K+ than it is to Na+
To generate an AP the membrane becomes more permeable to Na+
To end the AP (so a new one can be generated) the membrane again becomes more permeable to K+

2

Both channel types are

Highly specific for what ion is allowed to pass through

3

Depolarization

Na+ will Move down its concentration gradient into the cell (Na+ influx)
Na+ brings its positive charge with it, creating intracellular positivity

When Na+ channels close influx stops

4

In nerve and skeletal tissue

An excitatory stimulus (chemical binding or voltage change) will cause Na+ channels to open

Occurs at RMP, the cell is polarized

5

Full AP

1. Cell is at RMP, then receives an excitatory stimulus
2. Voltage opens some Na+ channels; allowing Na+ influx and the cell gradually becomes more positive/less negative
3. Voltage allows many Na+ channels to open; allowing an increase in Na+ influx creating a steep incline (spike potential)
4. Na+ channels close and K+ channels open, allowing K+ eflux; the cell becomes more negative/less positive
5. Excess K+ eflux
6. The Na+/K+ pump begins to actively pull K+ back into the cell to restore RMP

6

Chemically gated ion channels

Open or close when a chemical binds to a protien receptor that is part of the ion channel

Ex: Ach (Acetylcholine) is a neurotransmitter that causes Na+ channels to open

7

Muscle contraction is the summation of

Many APs (all phases)

8

At about the same time that Na+ channels close

K+ channels open

9

The ion will move into or out of the cell based on

It's concentration gradient (always down)

10

Voltage gated ion channel

Open or close in response to voltage changes
(membrane becoming more positive or negative)

11

Hyperpolarization

A brief period when excess K+ leaves the cell and the membrane temporarily becomes more negative than it was at rest

12

Repolarization

K+ will move down its concentration gradient out of the cell (K+ eflux)
K+ takes its positive charge with it creating intracellular negativity

13

AP trace

Represents the voltage across the cell membrane
Measured by comparing the charge of the ICF to the ECF

Technique is called "patch clamping"
Branch of science is called "electrophysiology"

14

Permeability changes are due to

The opening of protien ion channels in the membrane

15

AP

The reversal of the resting membrane potential such that the inside of the cell becomes more positive

16

Excitable tissue

Only contracts in response to electrical activity on the surface of the muscle cell membrane

17

Epimysium

Dense connective tissue layer around the whole muscle
Also called fascia

18

Microscopic general characteristics

Each fiber is a long cylindrical cell with multiple oval nuclei
Each muscle fiber is made of many myofibrils

19

Motor unit

One motor neuron + all the muscle fibers it innervates

20

Perimysium

CT covering around the bundles of muscle fibers called fasciles

21

Sarcoplasm

Intracellular fluid
Contains glycosomes and myoglobin

22

Tropomyosin

Stabilizing protien that winds along a groove in the F-actin strand

23

General functions of muscle

Body movement (skeletal)
Maintenance of posture (skeletal)
Production of heat as a by product of activity (all)
Constriction of organs and blood vessels (smooth)
Production of heart beat (cardiac)

24

Glycosomes

Store glycogen for energy

25

Hinge region

Junction of the head and the tail
Allows the head to bend and straighten during contraction

26

Transverse tubule (T-Tubule)

Invagination of the muscle cell sarcolemma
Runs between lateral spaces to form a triad (1 t tubule+2 lateral sacs= a triad)
Functions to quickly transmit AP through out the muscle cell

The AP signals the release of Ca+2 from the lateral sacs

27

Gross anatomy

Connective tissue
Neural innervation

28

Sarcomer

Structural units of actin and myosin
Functional unit of a muscle

Extends from one Z-disk to another
Striations can be seen under a microscope due to alternating light and dark bands

A bands
I bands
H zone
M line

29

Sarcolemma

Plasma membrane

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