QUT: PYB102

Divisions of Nervous System

Divisions of Nervous System

• Central Nervous System

• Peripheral Nervous System

Tracts

Bundle of axons in the CNS (white matter)

Nerves

Bundle of axons in the PNS (grey matter)

Nuclei

Groups of neuron cell bodies in the CNS (grey matter)

Ganglia

Groups of neuron cell bodies in PNS

Horizontal Plane

Sagittal Plane

Coronal Plane

Dorsal

Posterior

Ventral

Anterior

Medial

Lateral

Divisions of forebrain

Telencephalon and diencephalon

Telencephalon

Includes cerebral cortex, limb if system, basal ganglia

Diencephalon

Includes thalamus and hypothalamus

Midbrain

Includes the superior colliculi and inferior colliculi

Hindbrain

Includes medulla, pons, cerebellum, reticular formation

embryonic vesicles

Neural plate—> neural crest —> neural tube to form vesicles which develop major brain regions

Medulla

• Contains circuits of neurons which control functions vital for survival like HR BP and respiration

Pons

• bridge of fibres which connect brain stem with cerebellum

• Several nuclei clusters

• One cluster is reticular formation which influence consciousness and alertness

Cerebellum

• critical for movement and balance

Superior (anterior) colliculi

• relay visual info

• Important for visual attention

Inferior (posterior) colliculi

• Relay auditory info

• important for auditory attention

Colliculi

• appear as pair small bumps on dorsal surface of brain stem

Thalamus

• relay station for all sensory info except smell

• Filters and organises input

• Two little avocados

Hypothalamus

• major role regulating basic drives hunger and thirst

• Controls automatic NS and Body temp

• Controls pituitary gland

• 4 Fs (fighting fleeing feeding fucking)

• Regulates through NS bad endocrine

• Connected to pituitary gland

Limbic system

• learning memory and emotional expression

• Loosely connected structural network

• Includes hippocampus and amygdala

Amygdala

• important role processing emotional info and learning fear response

• In front of hippocampus

Hippocampus

• important role in memory, particularly consolidation

Cerebral cortex

• outer layer cerebral hemispheres

• Bumps on surface are gyrus/ gyri

• Groove on surface are sulcus/ sulci

Occipital lobes

• back of brain

• Includes primary visual cortex

• Vision

Parietal lobes

• behind central sulcus (big mid one)

• Perception of stimuli—> touch pressure temp pain

• Body sensory info

Temporal lobes

• below lateral fissure

• Perception and recognition auditory and memory

Frontal lobes

• Reasoning, planning, speech, movement, emotions, problem solving

Prefrontal cortex

• cortical area

• Problem solving, emotion, complex thought, higher order cognitive functions

Primary motor cortex

• cortical area

• Initiation of voluntary movement

Motor association cortex

• cortical area

• Coordination of complex movement

Primary somatosensory cortex

• cortical area

• Receives tactile information from body

• Somatotopic organisation

Sensory association area

• cortical area

• Processing multisensory info

Visual cortex

• cortical area

• Detection of simple visual stimuli

Visual association cortex

• Cortical area

• complex processing of visual info

Auditory cortex

• cortical area

• Detection of sound quality—> tone and loudness

Auditory association area

• cortical area

• Complex processing of auditory information

Wernicke’s area

• cortical area

• Comprehension of language

Broca’s area

• cortical area

• Speech production

Association areas

• primary area sends info to adjacent association cortex to analyse

• If close to primary sensor, only info from one sensor, further means info from more sensors

Corpus callosum

• important for communication between hemispheres, not only one but vital

• Located between in middle

Lateralisation

• localisation of function on one side of brain compared to other

• Specialised side

Contralateral arrangement

• motor cortex of each cerebral hemisphere mainly responsible movements on opposite side of body

Split Brain Experiment

• epilepsy patients with severed corpus callosum

• Found left hemisphere lateralised for speech

• Right hemisphere could display what say through identifying and picking up object

Cerebral ventricles

• chambers with CSF

• Ventricular system

• Lateral third and fourth ventricles

CSF ventricular circulation function

• mechanical shock absorber, protect brain sudden movement

• Medium for nutrient blood vessel and brain tissue exchange

• Buoyancy to make brain lighter

Vascular system

• brain depends on blood supply

• Brain capillaries greater resistance than others

• blood brain barrier

Blood brain barrier

• protective mechanism to protect brain from infections/ blood borne toxins

• Makes drug delivery to brain difficult

Meninges

• protective sheaths around brain and spinal cord

• Three layers: dura mater, arachnoid membrane, pia mater

Subarachnoid space

• Between pia mater and arachnoid, gap filled with CSF

Spinal cord

• motor signals to brain voluntary muscles

• Collect sensory info from body, somatosensory info, take to brain to process

• Protected by vertebral column and passes through hole in vertibrae

• At lumbar region just mass of spinal nerves

Afferent Axons

• arrive to spinal cord

• Dorsal

Efferent axons

• exit spinal cord

• Ventral

Somatic Nervous System

• carry motor info out and sensory in

• Spinal and cranial nerves

Spinal nerves

• each nerve consists fusion of two branches (roots)

• Spinal nerves begin at junction dorsal/ventral roots spinal cord

• Nerves leave vertebral column and travel to muscles or sensory receptors

Cranial nerves

• twelve pairs of cranial nerves attached to ventral surface of brain

• Most serve sensory and motor function head/ neck rroom

• Tenth/vagus nerve regulates function of organs in thoracic and abdominal cavities

Autonomic nervous system

• carries signals support basic life functions

• Activated two sub divisions: sympathetic NS and parasympathetic NS

Sympathetic NS

• involves activities associated with energy expenditure

• Fight or flight

• Dilated pupils, relaxed bronchi, accelerate and strengthen heartbeat, inhibits digestions, contracts vessels

Parasympathetic NS

• associated with increased energy supply

• Rest and digest

• Contract pupils, constricts bronchi, slows heartbeat, stimulates digestive, dilated vessels

Neurons

• basic NS functional units

• Take info from other neurons (reception) integrate signals (conduction) and pass signals to others (transmission

Glial cells

• nourish, protect, physically support neurons and though to be critical for brain development

Oligodenrocyte

• glial cell

• Covers axons of neurons with myelin—> substance critical to effective brain functioning

Dendrites

• receive messages

• Transmit info to soma

Soma (cell body)

• contains mechanisms that control metabolism/ cell maintenance

• Collate messages

Axon

• carries messages away from soma to cells with which neuron communicates

• messages called action potentials

Terminal buttons

• located end of twigs that branch of axons

• Secrete neurotransmitters which affect activity of other cells neuron communicating with

Myelin

• insulated axons to promote efficient transmission of action potential

• Increase speed of action potential propagation along axon

Neuron cell membrane

• made of lipid bilayer: two layers of fatty molecules

• Embedded protein molecules form pore/channel for material movement

• Not transmitting? Pores closed

Neuron at rest

• more sodium ions outside cell than inside

• More potassium ions inside cell than outside

• Resting potential neuron -70mV

Action potential

• brief reversal resting neuron charge

• When membrane sufficiently depolarised (resting potential moves towards 0)

• Threshold -55mV, no reach no action potential

• All or none

Action potential process

• Sodium channels open, enter reversing membrane potential

• Potassium channels open, leave restoring potential

• Ion transporters pump both back to original locations

• Action potential

Speed of action potential

• determined by diameter of axon (bigger faster)

• Presence/ absence myelin sheath (faster when there)

Myelin sheath properties

• electrical insulator, prevents ion flow across

• Ions only cross at breaks (nodes of ranvier)

• Sodium concentrated at nodes, action potential only generated in gaps

• Jumping from break to break increase speed

Synaptic transmission

• when AP at peak release specialised chemicals (neurotransmitters) travel across cleft and received by dendrites

• Sent is presynaptic receive is post synaptic

Release of neurotransmitters from terminal button stage 1

• before AP arrive neurotransmitters stored in vesicles within terminal button

Release of neurotransmitters from terminal button stage 2

• action potential triggers release of neurotransmitter into synaptic cleft

Release of neurotransmitters from terminal button stage 3

• neurotransmitters diffuse across synaptic cleft

• Some attach to receptor molecules in postsynaptic membrane and activate them either inhibiting or enabling postsynaptic neuron to generate an AP

Otto Loewi Experiment

• vagus nerve and cardiac muscle

• Hearts in solution only one physical connected

• Unconnected second heart also stimulated

• this could only happen if vagus nerve happened through chemical/molecular process

Neurotransmitter

• generic

• If transmitter binds with receptor and depolarises then it is excitatory and increases likelihood of AP

• If hyper-polarises membrane then inhibitory and makes AP less likely

Acetycholine (ACh)

• Neurotransmitter

• Activates motor neurons controlling skeletal muscles

• Contributes to regulation of attention arousal and memory

Dopamine (DA)

• Neurotransmitter

• Contributes to control of voluntary movement

• Important in reward motivation and pleasurable emotions

Serotonin (5-HT)

• Neurotransmitter

• Important in emotional states impulsiveness and dreaming

GABA

• Neurotransmitter

• Serves as widely distributed inhibitory transmitter

Endorphins

• Neurotransmitter

• Resemble opiate drugs in structure and effect

• Contribute to pain relief and some pleasurable emotions

Basic memory processes

• encoding

• Storage

• Retrieval

Encoding

• transform sensory stimuli into form that can be placed in memory

• Cherry 1953 cocktail party filter

• Assumptions: stimuli processed in parallel, one stimulus allowed through while others buffered, prevents system overload

Storage

• effectively retaining info for later use

Retrieval

• locating the item and using it recall be recognition

• Primacy effect: best for things learned first

• Recency effect: good for things learned last

• Context: memory better in context you learned

Role of attention

• determines encoding quality

• Maintenance rehearsal: role of repetition of info, without transformation into more meaningful code

• Elaborate rehearsal: meaningful processing of info

Enrich encoding

• visual imagery, concrete objects recalled better than abstract

• Self referent encoding, applying info to own self

Sensory register

• storage system that registers and briefly holds info from senses

• Iconic memory

• Echoic memory

Iconic memory

• related to visual system

• < ½ second duration

• 9-10 items (sperling 1960)