Mod4-Obj1: The cerebrum Flashcards
The cerebrum
Largest part of the brain
- Divided along the midline into two hemispheres by the longitudinal fissure
- Separated from the cerebellum by the transverse fissure
Cerebrum
Characterised by ridges (gyrus, gryi) and grooves (sulcus, sulci), increases the surface area, thus its functional capacity
-Each hemisphere is divided by sulci into five lobes: Frontal, parietal, temporal, occipital and insula
Cerebral hemispheres
Each hemisphere is divided into structurally and functionally distinct regions
Cerebral hemisphere: Gray matter
An outer layer of gray matter (2-4mm thick) cortex (neuron cell bodies)
Cerebral hemispheres: white matter
A deeper region of white matter (fibres/axons)
Cerebral hemispheres: basal nuclei
Clusters of grey matter deep within the white matter
Cerebral cortex
Location of the conscious mind
- Conscious thought processes, intellectual functions, memory storage and processing
- Localises and interprets sensory input
- Regulation of skeletal muscle activity (voluntary motor area)
The cortex of each cerebral hemisphere has 3 functional areas
- ) Motor areas
- ) Sensory areas
- ) Association areas
The cortex of each hemisphere…
- Deals with the sensory and motor functions of the opposite (contralateral) side of the body
- Has distinct functions (lateralisation)
Hemispheric lateralisation
- 90% of people are represented by the diagram = left cerebral dominance
- 10% of people have the reverse = right cerebral dominance
Left-brain functions
- Analytic thought
- Logic
- Language
- Science and maths
Right-brain functions
- Holistic thought
- Intuition
- Creativity
- Art and music
The primary motor cortex
Pre-central gyrus of the frontal lobe
-Plans and initiates all voluntary motor activity
The primary motor cortex contains…
The cell bodies of upper motor neurons of somatic motor pathways
The primary motor cortex directs…
Movement of skeletal muscles via somatic motor pathways, which control the contralateral side of the body
Specific areas of the primary motor cortex are devoted to…
Controlling specific parts of the body
The amount of motor cortex devoted to controlling a body part is…
Indicative of the complexity and precision of the movements of the body
e. g.) hands and face
- More neurons involved the greater distributed of neurons in the motor cortex
The primary motor cortex: Premotor area (motor association area)
Co-ordinates muscles involved in learned motor activity, e.g.) typing
The motor cortex: Broca’s area
Located in the motor association area
- Co-ordinates the muscles involved in speech generation
- In only one hemisphere
The motor cortex
Frontal eye field
Located in the motor association area
-Co-ordinated muscles involved in eye movements
Each of the 3 areas of the motor cortex (association area):
- ) Contain “memory banks” for complex motor activities
- ) Co-ordinate the movement of several muscle groups
- ) Act via the primary motor cortex
Damage to the primary motor cortex:
e. g.) stoke (ischaemic tissue damage)
- Paralyses the skeletal muscles controlled by the damaged area-voluntary movements only, not reflexive movement (which usually only involves the spinal cord not the motor cortex)
Damage to the premotor cortex
Loss of motor skills programmed by the damaged region but discrete movements unhindered
e.g.) typing area damaged=unable to type quickly but able to make the same discrete movements-able to reprogram another set of premotor neurons (relearn the activity)
The sensory cortex
The primary sensory and association areas are located in parietal, temporal and occipital lobes
- Concerned with the conscious awareness of sensation
- Somatosensory (general sensory) stimuli e.g.) touch, pain ect.
- Special sensory stimuli e.g.) vision, taste
Sensory and association areas include:
- Primary somatosensory cortex
- Visual cortex
- Auditory cortec
- Olfactory and gustatory cortex
- Visceral sensory area
- Vestibular (equilibrium) cortex
- General interpretive are (Wernicke’s area)
The primary somatosensory cortex
Located in the post-central gyrus of the parietal lobes
-Information from one side of the body reaches the contalateral sensory cortex after passing through the thalamus
The primary somatosensory cortex: Receives somatosensory information via multi-neuron sensory pathways from…
- ) General sensory receptors in the skin (e.g. touch, pressure, vibration, pain, temperature)
- ) Proprioceptors in skeletal muscles, joints and tendons (body position)
Specific areas of the primary somatosensory cortex are devoted to analysing sensory information from specific body parts
- Stimulus destination indicates site of origin
- The amount of sensory cortex devoted to a particular body region is related to that region’s sensitivity
(i. e. the more sensory receptors an area has”greater sensitivity”a larger area of the cortex required to analyse incoming information)
The somatosensory association area
Located posterior to the primary somatosensory cortex in the parietal lobe
-Interprets incoming sensory information by comparing it to stored memories of past sensory experiences
Damage to the somatosensory association area…
Los the ability to identify objects by touch alone
-Need another sense such as visual information, to identify an object
Special sensory cortices: Visual areas-Occipital lobes
Visual cortex -Receives impulses from the retinas -Damage: functional blindness visual association area -Interprets visual images -Damage: Failure to recognise objects
Special sensory cortices: Auditory areas-Temporal lobes
Auditory cortex -Receives impulses from inner ear -Damage: deafness Auditory association area -Interprets auditory stimuli -Damage: failure to recognise what is heard
Special sensory cortices: Olfactory cortex-Temporal lobe
Conscious awareness of odour
Special sensory cortices: Gustatory cortex-Insula (deep to the temporal lobe)
Perception of taste stimuli
Special sensory cortices: Visceral cortex-Insula
Perception of visceral sensations
e.g.) upset stomach, full bladder
Special sensory cortices: Vestibular (equilibrium) cortex-insula
Awareness of balance
General interpretive area: Wenicke’s area
Generally in the left temporal lobe (same side as Broca’s area)
- Linked to Broca’s area (motor speech area)
- Integrates information from sensory, visual and auditory areas
- Recognition and understanding of spoken and written language
Damage to Wernicke’s area
Affects ability to interpret visual and auditory information
i.e.) aphasia (inability to understand language or even speak, read and write)
Multimodal association area
Located in the prefrontal cortex
- Most complicated cortical area
- Coordinates information from all association areas
Multimodal association area is involved in…
intellect, complex learning abilities, recall and personality
- Working memory-abstract ideas, judgement, reasoning, planning
- Maturation associated with environmental interaction over time
Cerebral white matter
Responsible for communication between hemispheres and between the cerebral cortex and other CNS areas
-Predominantly made up of myelinated fibre tracts
Cerebral white matter: Commissures
Connect the two hemispheres
e.g.) corpus callosum
Cerebral white matter: Association fibres
Connect different parts of the same hemisphere
Cerebral white matter: Projection fibres
Connect cerebral cortex with other CNS areas
Cerebral basal nuclei
Concentration of gray matter (nuclei) deep within each cerebral hemisphere
- Communicate with the motor areas of the cerebrum and cerebellum
- Help to control the intensity of skeletal muscle movements executed by the primary motor cortex-dampen muscle activity to facilitate smooth movement
Cerebral basal nuclei activity…
Regulated by the neurotransmitter dopamine (decreases basal nuclei activity)
- Overactivity: Movement impaired, e.g.) Parkinson’s disease
- Under-activity: Excessive movement, e.g.) Huntington’s disease
The cerebrum summary
Largest part of the brain, divided into 2 hemispheres each with similar and distinct functions
The cerebrum summary: functions of the cerebral cortex (gray matter)
- Conscious thought processes and intellectual functions
- Controlling voluntary skeletal muscle activity
- Localising and interpreting sensory input
- Emotional processing
- Memory processing and storage
The cerebrum summary: functions of the white matter include
Communication via fibre tracts
The cerebrum summary: functions of the basal nuclei
Control intensity of (dampen) skeletal muscle activity to facilitate smooth movement
