The Brain, Motor Control and Senses Flashcards
Lobes of the Brain
Frontal
Parietal
Occipital
Temporal
Regions of the Brain
Cerebrum
Diencephalon
Brainstem
Cerebellum
- Cerebrum consists of right & left hemispheres
- Central core - diencephalon
- Cerebral hemispheres consist of cerebral cortex
- Cerebral cortex is outer shell of grey matter
- Inner part of cerebral cortex is layer of white matter
- Within grey matter are subcortical nuclei (important for movement/posture)
Forebrain
- Each cortex connected by bundle of nerve fibres - corpus callosum
- Ridges - gyri
- Grooves - sulci
- Integrating area:
- Basic afferent information processed
- Control over systems that govern movement
- Cells:
- Pyramidal
- Non-pyramidal
Cerebrum
Diencephalon contains and is responsible for:
- Thalamus - arousal, movement, attention
- Hypothalamus - neural and endocrine
- Important centre for coordinating movements & controlling posture & balance
- Receives info from muscles, joints, eyes, skin, ears & parts of brain controlling movement
- Implicated in some forms of learning
Cerebellum
- All nerve fibres that relay signals between forebrain, cerebellum and spinal cord pass through.
- Contains reticular formation:
- Motor functions
- CV, respiratory, swallowing
- Sleep, attention, eye movement
- Receives and integrates input from all regions of CNS
Brainstem
- Membranes that line the structures
- Add additional support and protection:
* Dura mater
* Arachnoid mater
* Pia mater - Function:
* Cover & protect CNS
* Protect blood vessels
* Contain cerebrospinal fluid
* Form partitions in skull
Meninges
What is the Blood Brain Barrier?
Protective mechanism that helps maintain a stable environment for the brain.
Motor Control Hierarchy
- General intention at highest level of hierarchy
- Info relayed to middle level structures
- Receive afferent information from receptors on muscle, tendon, joints, skin, etc.
- Accompanied by a conscious awareness
- Attention directed toward purpose
Voluntary movement
- Unconscious
- Automatic
Involuntary movement
Sensory Receptors
- Mechanoreceptors
- Thermoreceptors
- Photoreceptors
- Chemoreceptors
- Nociceptors
- Compromise 90% of spinal neurons
- Integrate information from higher centres and peripheral receptors
- Crucial for coordinating repetitive, rhythmical movements
- Can be turned on or off
Interneurons
Withdrawal reflex
1 - Stimulus
2 - Pain detected by nociceptor and signal sent to CNS
3 - Extensor muscle relaxes due to inhibitory synapse
4 - Flexor muscle contracts due to excitatory muscle
5 - Stand up on other leg
6 - Signal sent to brain
Stretch Reflex - Knee Jerk
1 - Tap 2 - Tendon pushed in 3 - Thigh muscle stretched 4 - Muscle spindle activated 5 - AP afferent neuron 6 - Excitatory synapse 7 - Thigh contracts 8 - Knee jerks
Decreased levels of attention - EEG
Alpha rhythm
Increased levels of attention - EEG
Beta rhythm
Peripheral endings of afferent nerve fibers wrapped around modified muscle fibers. What does it monitor?
Muscle Spindle. Monitors muscle length and rate of change in length.
Endings of afferent nerve fibers that wrap around collagen bundles in tendons. What does it monitor?
Golgi Tendon Organ. Tension.
What does tension depend on?
- Muscle length
- Load on the muscle
- Fatigue
- Transduction process involving opening/closing of ion channels
- Ion flux results in a change in membrane potential
- Current flows to a region where there are voltage-gated channels
Receptor potential
Conversion of a stimulus into a signal that conveys the relevant information
Primary sensory coding
Important characteristics for primary sensory coding
- Type of energy it represents
- Intensity
- Location of body it affects
The area that when stimulated, leads to activity in a particular afferent neuron
Receptive field
Stimulus location of vision, hearing and smell
Interpreted as outside the body
Stimulus location coded for by…
Site of stimulated receptor and pathways of APs
Factors that affect stimulus location:
- Size of receptive field
- Density of sensory units
- Overlap between receptive fields
A neuron responds most vigorously when…
Stimulus is in middle of receptive field
What happens when strength of stimulus increases?
Receptors on adjacent branches of an afferent neuron are activated, resulting in summation
- Enables localisation of a stimulus site for some sensory systems
- Information from afferent neurons whose receptors are at the edge of a stimulus is strongly inhibited
- Enhances the contrast between the centre and periphery of stimulated region
Lateral inhibition
