the structure and function of the brain

The Structure and Function of the BrainLesson 5

Sunday, 29 January 2012

Lesson 4: The Neuron

Exam Question

a) Label the diagram below (1 mark)

b) Describe how a neuron transmits information. (3 marks)


a) 1. Synaptic Knob 2. Myelin Sheath 3. Axon 4. Node of Ranvier5. Soma (cell body)6. Dendrites7. Nucleus

b) A neuron transmits information by creating an action potential. When a neuron is stimulated, channels in its membrane open, briefly allowing positively charged sodium ions to rush in, this creates a change in electrical activity leading to an action potential.


Lobes of the Brain


Cerebral Cortex

The cerebral cortex is the thin (3-5 mm thick) convoluted (folded) outer layer of the brain.The value of the folding is that it enables a greater surface area of cerebral cortex to be contained within the skull; this gives a greater volume and enables the cerebral cortex to contain more neurons and more blood-vessels to get more oxygen and glucose (for energy) to this most fuel-hungry part of the body.

There are three main types of functional areas in the cerebral cortex:

1. the sensory areas which receive information provided by the various senses (especially touch, vision, and hearing);2. The motor cortex which sends information to muscles so they can create bodily movements3. The association areas which integrate sensory and motor information and are involved with information processing activities such as language and speech, learning, memory, thinking and problem solving


Frontal Lobe

The frontal lobes are the largest lobes and occur on the top front halves of the cerebral hemispheres. The primary motor cortex is at the back of the

frontal lobes. It runs across the top of the brain from left to right.

It is divided by the longitudinal fissure that separates the two hemispheres.

Specific areas of the motor cortex are responsible for the movement of particular body parts.

· Right Controls Left/Left Controls Right· Top Controls Bottom/Bottom Controls Top


Motor homunculus— represents the body parts in terms of the relative size of the area each of body part occupies along the primary

motor cortex.


Association Areas in Frontal Lobe

Broca’s Area: the “Speech Production Centre” is part of the association cortex. It is located in the left frontal lobe and is involved with the production of clear, fluent speech. Broca’s area helps us with the structure of sentences and parts of speech such as adjectives, prepositions and conjunctions. Broca’s area is involved

with analysing the grammatical structure of sentences that we hear as well as those that we speak.

Other association cortex in the frontal lobes is involved in

ReasoningPlanningThinking


Parietal Lobe

The parietal lobes are located on the top central part of the brain. Primary Areas in the Parietal Lobes – The Primary Somatosensory Cortex

The primary somatosensory cortex is at the rear of the central fissure, immediately opposite the primary motor cortex.

The primary somatosensory cortex registers the sense of touch, by receiving information about pressure, pain, temperature, muscle movement and position from sensory receptors around the

body

It is divided by the longitudinal fissure that separates the two hemispheres.

Specific areas of the primary somatosensory cortex receive sensations from particular parts of the body.

· Right Receives From Left/Left Receives From Right· Top Receives From Bottom/Bottom Receives From Top


Sensory homunculus—Similar to motor homunculus but it tells the brain how much power is needed for sensory

perception of different body parts.


Association Areas in Parietal Lobe

The association cortex of the parietal lobes is important in

Integrating visual informationMonitoring the body’s position in space

Determining where objects are located in space.


Temporal Lobe

Primary Area in the Temporal Lobes – The Primary Auditory Cortex

Auditory – sound – information is sent to the primary auditory cortex, located slightly above and in front of the

ears.


Association Areas in Temporal Lobe

Wernicke’s area - the “Speech Reception Centre” is part of the association cortex. It is located in the left temporal lobe and is involved with the reception and comprehension of speech.

* Stores the receptor codes for language or enables comprehension of speech/language

* Enables interpretation of the written word

* Is used for locating words from memory to express a particular meaning

* Is used for creating meaningful and/or grammatically correct speech

Other association cortex of the temporal lobes is important in

Memory - the ability to remember facesStoring of episodic memories such as our first day at school or a particular

holidayRecognition of objects


Occipital Lobe

Primary Area in the Occipital Lobes – The Primary Visual Cortex

Visual information from the eyes is sent to the Primary Visual Cortex in the occipital lobe at the back of each cerebral

hemisphere.


Association Areas in Occipital Lobe

The association cortex of the occipital lobes is important in

Selection, organisation and integration of features of visual stimuli.


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