Neural (Nervous) Tissue

Front 1

What are the functions of the nervous tissue?

Back 1

1. sensing changes with sensory receptors (sensation)
2. interpreting and remembering changes (integration)
3. reacting to those changes with effectors

Front 2

what are the 2 types of ion channels?

Back 2

1. Leakage (non-gated) channel
2. Gated channel:
a. voltage-gated
b. chemically-gated (ligand-gated)
c. mechanically-gated

Front 3

what are properties of leakage (non-gated) channel?

Back 3

- always open (passive)
- nerve cells have more K+ than Na+ leakage channels
- therefore, membrane permeability to K+ is higher
- resting membrane potential in nerve tissue is -70mV

Front 4

what are properties of gated channel?

Back 4

they open and close in response to stimulus results in neuron excitability
1. voltage-gated channel: open/close in response to change in voltage
2. chem.-gated (ligand-gated):
open/close in response to change in chemical stimuli (hormone, neurotransmitter, ion).
3. mechanically-gated channel: open/close due to mechanical stimulation (pressure, stretching, vibration)

Front 5

what is resting membrane potential?

Back 5

= negative ions along inside of cell membrane and positive ions along the outside cell membrane.

* potential energy difference at rest is -70mV.

Front 6

why do resting membrane potential exist?

Back 6

1. because concentration of ions different inside and outside the cell membrane
* ECF is rich in Na+ and Cl-
* cytosol full of K+, organic
phosphate and amino acids

2. Because membrane permeability is different for K+ and Na+.
* permeability for K+ is 50-100 greater
* inflow of Na+ can't keep up with outflow of K+
* Na+/K+ pump remove Na+ as fast as it leaks in

Front 7

what are graded potentials?

Back 7

- hyperpolarization= membrane becomes more negative
- depolarization= membrane becomes more positive (less negative)

Front 8

what are local potentials?

Back 8

- local disturbances in membrane potential
- aka. graded potential, caused by depolarizing of inside plasma membrane
- depolarization decreases potential across cell membrane due to opening of gated Na+ channels

Front 9

Local Potential vs action potential

Back 9

- local potential are graded (vary in magnitude depending w. stimulus strength)
- local potentials a decremental (get weaker the farther they spread)
- local potentials are reversible once K+ diffused out of cell
- local potentials can either be excitatory/inhibitory (causing it to hyper-polarize)

Front 10

How do graded potential arise?

Back 10

1. From source of stimuli:
- mechanical: pressure at the ion channels
- chemical: neurotransmitter at ligand-gated ion channels
2. Graded/post-synaptic/ receptor/generator potential:
- ions flow via ion channels and change membrane potential locally
- amount of change varies with strength of stimuli
3. Flow of ions (current) creates local change only