Cerebral Hemispheres

• Gyri, Sulci & Fissures

  elevated ridges of tissue = gyri

  separate by shallow grooves = sulci

  deeper grooves = fissures, separate large regions of the brain
• Median Longitudinal Fissure

  median longitudinal fissure separates the cerbral hemispheres

  
• Transverse Cerebral Fissure

  transverse cerebral fissure separates the cerbral hemispheres from the cerebellum
• Regions of Cerebral Hemispheres

  a superficial cerbral cortex of grey matter

  internal white matter

  basal nuclei, islands of grey matter, situated deep w in the white matter
• Cerebral Cortex

  cerebral cortex = executive suite of the nervous system, where our conscious mindcerebral cortex = executive suite of the nervous system, where our conscious mindcerebral cortex = executive suite of the nervous system, where our conscious mindcerebral cortex = executive suite of the nervous system, where our conscious mind

  enables us to be aware of ourselves + sensation, to communicate, remember, understand + initate voluntary movements
• Composition of Cerbral Cortex

  the cerebral cortex is composed of grey matter

  = neuron cell bodies, dendrites, associated glia + blood vessels but no fibre tracts

  contains billions of neurons arranged in 6 layers
• Functional Areas of the Cerebral Cortex

  the cerebral cortex contains 3 functional areas:

  motor

  sensory

  association

  each hemisphere is chiefly concerned w the sensory + motor functions of the contralateral (opposite) side of the body

  altho largely symetrical in structure, the 2 hemispheres r not entirely equal in function

  instead there is specialisation of cortical functions
• Motor Areas of the Cortex


  the motor areas of the cortex, control voluntary movement, lie in the part of the frontal lobes - primary motor cortex, premotor cortex, Broca's area + frontal eye field
• Primaray Motor Cortex


  the primary motor cortex is located in the precental gyrus of the frontal lobe of each hemisphere

  large neurons, called pyramidal cells, allows us to consciouly control the precise/skilled voluntary movements of our skeletal muscles

  
• Primary Motor Cortex - Pyramidal Cells

  pyramidal cells = large neurons that allow us to consciously contorl the precise/skilled voluntary movements of our skeletal muscles

  their long axons, which project to the spinal cord, form the massive voluntary motor tracts = pyramidal tracts

  all other descending motor tracts come from brain stem nuclei + consists of chains of 2 or more neurons
• Somatotopy

  the entire body is represented spatially in the primary motor cortex of each hemishphere

  e.g. the pyramidal cells that control foot movements r in one place + those that control hand movements r in another

  such mapping og the body in CNS structures = somatotopy
• Cerebral Hemispheres


  the 2 cerebral hemispheres of the brain r almost identical + r connected by the corpus callusum

  = wide, flat heavily meyelinated axon bundle

  
• Gross Anatomy of the Brain

  the human brain has a no fo divisions:

  cerebral hemispheres, diencephalon (thalamus, hypothalamus), brainstem + cerebellum

  there is a unique distibution of grey + white matter thru out the brain

  grey matter - short unmyleinated neurons + neuron cell bodies

  white matter - mostly myleinated axons which form sensory + motor tracts

  
• Frontal Lobe


  forms the anterior part of each hemisphere + is borded posteriorly by the central sulcus + inferiorly by the lateral sulcus

  
• Parietal Lobe


  posterior to the frontal lobe, separated by the central sulcus

  
• Temporal Lobe


  inferior to frontal + parietal lobes

  separated from them by the lateral sulcus

  
• Occipital Lobe


  posterior part of each hemisphere

  no sulci separate the occipital lobe from other lobes

  
• Insula


  lies deep inside the lateral sulcus + is separated from other lobes by a circular sulcus

  
• Premotor Cortex


  just anterior to the precentral gyrus in the frontal lobe is the premotor cortex

  the premotor cortex helps plan movements

  this region selects + sequences basic motor movements into more complex tasks, like typing

  coordinates the movement of several muscle groups simultaneously/sequentially, mainly by sending activating impulses to the primary motor cortex
• Premotor Cortex


  coordinates movement of several muscle groups

  
• Broca's Area


  Broca's area lies anterior to the inferior region of the inferior region of the premotor area

  only present in the left hemisphere

  special motor speech area that directs the muscles involved in sppech production

  also becomes active as wer prepare to speak
• Broca's Area


  special motor speech area

  
• Frontal Eye Field

  the frontal eye field is located partially in + anterior to the premotor cortex + superior to Broca's area

  this cortical region controls voluntary movement of the eyes

  
• Orbital Cortex


  emotional processing + behaviour control thru emotional reward

  
• Sensory Areas


  areas concerned w conscious awareness of sensation, the sensory areas of the cortex, occur in the parietal, insula, temporal + occipital lobes
• Primary Somatosensory Cortex


  the primary somatosensory cortex resides in the postcentral gyrus of the parietal lobe, just posterior to the primary motor cortex

  neurons in this gyrus receive info from the general sensory receptors in the skin + from propioceptors

  
• Primary Somatosensory Cortex - Proprioceptors

  propioceptors, located in skeletal muscles, joints + tendons inform the brain of the body's position in space

  the neurons then identify the body region being stimulated, an ability = spatial discrimination
• Somatosensory Association Cortex


  the somatosensory association cortex lies just posterior to the primary somatosensory cortex + has many connections w it

  the major function of this area is to integrate sensory inputs ( temp, pressure ...) relayed to it via the primary somatosensory cortex to produce an understanding of an object being felt -size, texture + relationship of its parts

  
• Primary Visual Cortex


  the primary visual cortex is seen on the extreme posterior tip of the occipital lobe

  largest cortical sensory area

  receives visual info that originates from the retina

  the visual space on the opposite side of the body is mapped onto the somatosensory cortex

  
• Visual Asociation Area

  the visual association area surrounds the primary visual cortex + covers much of the occipital lobe

  communicating w the primary visual cortex, the visual association area uses past visual experiences to interpret visual stimuli, enabling us to recognise ppl + objects

  = done by cortical neurons

  complex visual processing involves the entire posterior half of the cerebral hemispheres

  
• Primary Auditory Cortex


  each primary auditory cortex is located in the superior margin of the temporal lobe next to the lateral sulcus

  sound energy exciting the hearing receptors of the inner ear causes impulses to be transmitted to the primary auditory cortex, where they r interpreted as pitch, loudness + location

  
• Auditory Association Area


  the more posterior auditory association area then permits the perception of the sound stimulus, which we hear as speech, scream, music....

  memories of sounds heard in the past appear to be stored here