Sensory

Question 1

Second order neurons in the “through pathway” are namely bipolar cells what are the types and what are they valuable for?

Answer 1

1 x rods, 9 cones and they are important for colour and spatial vision.

Question 2

What are the features of ganglion cells?

Answer 2

Last cells in the though pathway about 23 different types, break down information into finite units, they have four types ON, OFF, M and P. Only neuron in the Retina that fires AP due to their requirement of signalling across long distances.

Question 3

Describe the Receptive field properties of a Ganglion cell

Answer 3

Ganglion cells depolarise light by either increasing or decreasing their AP firing rate. The receptive field of a ganglion cell is the area in the retinat that wehn stimulated with light changes the cell’s membrane potential and it fires. Ganglia cells will change their way of firing depending on where in the receptive field you stimulate. They can activate antagonistic centre.s

Question 4

How can the response of a ganglion cell change and integrate information over time?

Answer 4

Sudden burst of APS at the onset of the stimulus (transient) and sustained through continous APs during stimulation.

Question 5

How do Ganglion cells convery parallel information?

Answer 5

20 different ganglion cells with 20 different channels of infromation. The different receptor fields properties are the ways in which the image is decoded. Ganglion cells response through increase or decrease in firing or through transient or sustained responses.

Question 6

Describe the lateral inhibitions of the through pathway.

Answer 6

Horizontal cells: GABA–» respond to light by hyperpolarising–> receive input and coney output onto photoreceptors.
Amarcirne cells: Axonless cells, input from bipolar cells and output on the ganglion cells they usually are important in motion detection and horizontal cells are important in setting up the receptor field. (35-40 different types. Can use glycine and GABA

Question 7

Describe the output neurons on the retina.

Answer 7

M (parasol) ganglion cells- magnocellular- large, large receptor field, detect motion, flicker and analysis of gross features. (5%) The P ganglion cells more numerous - visual acuity and colour vision (smaller receptor field)- 95%
Both are colour responsive.

Question 8

Outline the visual pathway

Answer 8

Retina—> Optic nerve—LGN–> Optic radiations—> Visual cortex

Question 9

Describe the optic chiasm

Answer 9

Fibres from left and right optic nerve—> form at the base of the pituary. Near you internal carotid arteries (main blood supply to your head)

Question 10

Describe the arrangement of fibres in the lateral geniculate nucleus

Answer 10

Six layers, no integration of the streams of information. M cells (1-2) layers and P cells (3-6)

Question 11

Optic radiations description

Answer 11

White matter tract formed by the axons of the LGN neurons, large and thick they make the synapse in the PVC.

Question 12

The projection from the optic radiations is to V1 of the PVC describe the region and its anatomical arrangement

Answer 12

LGN project to the PVC, area 17, occiptal lobe around the calcarine fissure, each half of the visual field is represented by the contralateral VC. Retinotopic organsiation, neighbouring cells within the retina project ti its neighbouring cells in the LGN and Visual cortex.

Question 13

How is the PVC arranged in terms of input

Answer 13

6 layers of neurons and complexes.
Layer 4c is the input layer from the cortex all receive input from the thalamus in alter 4C where information enters the cortex.

Question 14

What are the cortical neurons in the VC responding to?

Answer 14

Orientation selectivity neruons are responding to bars of light at particular orientations

Question 15

Ocular dominance columns

Answer 15

Input from the LGN is segregated into small regions in the PVC called an ocular dominance coloutn

Question 16

Mixing inforomation

Answer 16

M type input to layer 4calpha and P type go to layer 4CBeta. Mixing of information occurs in layer IVB and Layer III

Question 17

Describe pathways beyond

Answer 17

Dorsal (pathway)- where - MT –MST

Ventral (What)pathway—V4—IT

Question 18

Dorsal stream

Answer 18

AREA MT (Layers V1,V2,V3)- detects motion

Question 19

Ventral stream

Answer 19

Where===) Colour detection, object recognition.

Question 20

Area IT

Answer 20

Input from V4–> respond to abstract shapes and colour- important for visual memory and perception and perception faces

Question 21

What is the function of the cochelea of the inner ear?

Answer 21

Spectral deposition- all different frequencies of sound that are coming are getting separated out into their individual frequencies.
As the fluid in these chambers is vibrating you get vibrates in synchorony. Small fibres vibrate at high frequencies. and fat fibres (base) at low frequencies.