SNS - Biology - Nervous System Flashcards Preview

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Flashcards in SNS - Biology - Nervous System Deck (26):
1


Invertebrates

Protozoa

Unicellular organisms possess no organized nervous system

May respond to stimuli including touch, heat, light and chemicals

2



Invertebrates

Cnidarians

Simple nervous system - nerve net

Network of nerve cells which may have limited centralisation

Some jellyfish have clusters of cells and pathways that coordinate the relatively complex movements required for swimming

3


Invertebrates

Annelida

Earthworms possess primitive nervous system consisting of defined ventral nerve chord and anterior 'brain' of fused ganglia

Definite nerve pathways lead from receptors to effectors

4


Invertebrates

Arthropoda

Brains similar to annelids but more specialised sense organs present (eg compound or simple eyes, tympanum for detecting sound)

5


Neuronal Resting Membrane Potential

-70mV

Inside of neuron more negative than outside

Due to selective ionic permeability of Na-K pump - uses ATP to transport 3 Na+ out for every 2K+ transported into the cell

Neuron is also selectively permeable to K+, allowing it to diffuse outwards along conc gradient, decresing neuronal resting potential

6

Neuronal Threshold Membrane Potential

Level at which an AP generated

Usually ~ -50mV

7


Action Potential Mechanism

  1. Soma receives excitatory and inhibitory impulses from other nerve cells
  2. Depolarised above threshold membrane potential, VGSCs open - Na+ enters further depolarising cell
  3. VGPCs open, VGSCs close, repolarises as K+ leaves cell
  4. Cell hyperpolarises
  5. VGPCs close, resting potential restored

8


Diameter and Action Potential Velocity

Greater the diameter, greater the speed of AP

9


Drugs and Synapses

Curare

Blocks postsynaptic ACh receptors

Leads to paralysis by blocking nerve impulses to muscles

10

Drugs and Synapses

Botulinium Toxin

Blocks presynaptic release of ACh

Resluts in paralysis

11


Drugs and Synapses

Anticholinesterases

Inhibit acetylcholinesterase

ACh not degraded at synapse and continues to act, preventing coordinated muscle contractions

Used as nerve gases and insecticides (parathion)

12


CNS

Brain

Forebrain

  1. Telencephalon - cerbral cortex, olfactory bulb
  2. Diencephalon - thalamus and hypothalamus

13

CNS

Brain

Mesencephalon

Midbrain

Relay centre for visual and auditory impulses

Important role in motor control

14


CNS

Brain

Hindbrain

Brainstem :

  1. Cerebellum - modulates motor impulses initiated by cerebral cortex and important in the maitentance of balance, hand eye coordination and timing of rapid movements
  2. Pons - relay centre between cortex and cerebellum
  3. Medulla - many functions including breathing, heart rate and GI activity

15


PNS

Divisions

  1. Somatic
  2. Autonomic : (A) Sympathetic, (B) Parasympathetic

16


The Eye

Sclera

Thick opaque layer covering the surface of the eyeball

17

The Eye

Choroid

Layer beneath the sclera

Helps to supply the retina with blood

Dark, pigmented area that reduces reflection in the eye

18

The Eye

Retina

Innermost layer

Contains the photoreceptors:

  1. Cone cells - respond to high intensity light, sensitive to colour. Contain three pigments that absorb red, blue and green wavelength
  2. Rods - respond to low intensity light, importnat in night vision. Contains a single pigment - rhodopsin - which absorbs single wavelength

These synapse with bipolar cells which synapse with ganglion cells. Axons of ganglion cells bundle into optic nerve

19

The Eye

Cornea

Transparent outer layer at front of eye

Bends and focuses light which then travel via the pupil through the lens suspended behind it and image forms on retina

20

The Eye

Iris

Pigmented. muscular structure

Controls pupil diameter

21


The Eye

Ciliary Muscles

Control the shape and focal length of the lens

22

The Eye

Blind Spot

Point at which the optic nerve exits the eye - photoreceptors not present

23

The Eye

Fovea

Small are of the retina, densely packed with cones

Important for high-acuity vision

24


The Eye

Vitreous Humour

Jellylike material which helps maintain shape and optical properties of eye

Is formed by the eye and exits it via ducts to join the venous blood

25


The Eye

1. Myopia

2. Hyperopia

3. Astigmatism

4. Cateracts

5. Glaucoma

  1. Nearsightedness - image focused in front of the retina
  2. Farsightedness - image focusd behind the retina
  3. Irregularly shaped cornea
  4. Lens becomes opaque, causing blindness
  5. Increased pressure in eye due to blockage of vitreous humor outflow

26


The Ear

1. Outer Ear

2. Middle Ear

3. Inner Ear

  1. Auricle, auditory canal
  2. Tympanic membrane, Ossicles (malleus, incus, stapes),Oval window
  3. Cochlea (contains hair cells and basillar membrane) , vestibular apparatus (maintains balance)

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