Nervous System, Spine And Brain Flashcards
Main function of the nervous system -
Detect changes in internal/external environments and therefore bring response in muscle,organs and glands
What are the two different nervous systems and what are they each made up of?
Central nervous system (CNS) - brain and spinal cord
Peripheral nervous system (PNS) - outside brain and spinal cord
Neurons, function and common characteristics:
Basic structural and function untis of the nervous system is the nerve cell/neuron
All neurons share these common characteristics:
Single cell body (soma)
Axon - allow AP’s to travel;
Dendrites - receive info (have neurotransmitters)
Synaptic terminals (axon terminals)
Myelin -
What are the gaps between myelin?
What forms myelin?
The insulting layer of axons
Made primarily of lipids
AP’s travel quickly and more effectively in myelinated compared to unmyelinated
Gapes between myelin is called the nodes of ranvier - contain sodium channels
Swchann cells form myelin - peripheral
Oligodendrocyte cells from myelin - CNS
Neurone types
Biopolar neurone -
Pseudounipolar neurone -
Multipolar -
Biopolar - sensory neurone (uncommon - found only in nasal cavity, retina and within ear)
Pseudounipolar - sensory neurone (cell body in centre of neurone)
Multipolar - motor neurone and inter neurones. Most common type in the CNS (cell body at end of neurone)
Motor neurones divided into two sub-division
1) upper motor neuron (UMN)
2) lower motor neuron (LMN)
1) upper - transmit info from brain to lower motor neurones and inter neurones in the brain stem and spinal cord. Part of the CNS
2) lower motor neurones- neurons with cell bodies in spinal cord or brain stem whose axons directly Innervation skeletal muscle. Part of PNS
White matter -
Grey matter -
Which does the CNS contain?
White - contains axons of the neurones (covered in myelin,fatty substance therefore is white) makes up 60% of brain
Grey - contains cell body of neurones (not covered in myelin) makes up 40% of brain
CNS has both grey and white matter
What are the three actions of the nervous system?
1 - receiving and transmitting sensory input (PNS)
2- centra processing/integration
3- motor output (PNS)
AP’s - nerve impulse
How is a neurone polarised ?
Body - electrically neutral. Some areas are more positive/negative than others
Currents indicate the flow of postive/negatively charged ions across the resistance of your cell membrane
Resting neurone is more negative inside
Resting potential - 70mv
Sodium ions sit outside
Potassium ions sit inside neurone, but there is less of them therefore outside is more positive than inside
Polarized - negative membrane potential
AP’s and nerve impulse
Role os sodium potassium pump =
2x potassium in cell and 3x sodium out of cell, therefore creates a concentration difference
This creates an electrochemical gradient
AP’s and nerve impulse
Ion channels - large proteins:
1) voltage-gated channels -
2) ligand-gated channels -
3) mechanically gated channels -
1) open and close in response to changes in membrane potential
2) open when neurotransmitter latches onto it’s receptor
3) open in response to physical stretching of the membrane
When open - ions flood in to even out electrochemical gradient
AP’s and nerve impulse
Stages of an AP -
Neurone must be depolarised for an AP to occur
1) resting -70mv. Ion channels are closed
2) stimulus occurs - sodium channels open therefore increasing charge inside membrane. -55mv is the threshold for an AP to occur - all or nothing law
3) if reached, voltage-gated sodium channels open therefore sodium floods in. +40mv reached - AP
4) repolarisation occurs - voltage gated potassium channels open and therefore flow out neurone
5) brief period of hyper-polarisation
6) all channels closed and resting restored
AP’s and nerve impulses
What is a refractory period?
A period whereby unable to respond to any other stimulus, no matter how strong.
Prevents signals travelling in two different directions down an axon at once
AP’s and nerve impulse
Why is myelin important ?
Synapse -
Myelin important as will conduct impulses faster
Synapse - the meeting point between two neurones. Converts APs to a different type of signal and sends it to another neurone. Some synapses are electrical - quickest
Others are chemical - takes longer but used more often and easier to control
Chemical uses neurotransmitters
AP’s and nerve impulse
What happens when an AP reaches a pre-synaptic terminal ?
Voltage gated calcium channels open and release calcium. Synaptic vesicles merge with membrane. Neurotransmitters released into synaptic cleft and bring to receptors on post synaptic neurone. Electrical is converted into chemical here
AP’s and nerve impulse
Summation -
Spatial -
Temporal -
Summation - process that determines if an action potential will be generated by the combined effects of excitory and inhibitory signals
Spatial - multiple simultaneous inputs
Temporal - repeated inputs
Depending on the total of the individual inputs, summation may/may not reach threshold voltage to trigger an AP.
Spinal cord
Myotomes -
Dermatomes -
Myotomes - group of muscles innovated by a single nerve route
Dermatomes - strip of skin innovated by single spinal nerve
What are the different categories of spinal processes and how many make up each?
Cervical spine - C1-C8
Thoracic spine - T1-T12
Lumbar spine - L1-L5
Sacral spine - S1-S5
Coccygeal nerve - C0
Name of hole in vertebrae -
Name of opening just posterior to where vertebrae are stacked on top of each other -
Vertebrae foreamen - spinal cord sits in this
Intervertebral foreamen - this I where spinal nerve routes emerge from spinal cord to innovate different areas/muscles
What protects the spinal cord?
Where does the cerebral spinal fluid sit?
Meninges - three dif ones
Pia mater - thinnest most inner one
Arachnoid matter - middle
Dura matter - outer
Fluid sits between the Pia and arachnoid (subarachnoid space) - liquid protection
Spinal tracts
Afferent-
Efferent -
Name the tracts that make up each:
Afferent - ascending SENSORY spinal tracts
Called -dorsal column, spinocerebellar, spinothalamic
Efferent - descending MOTOR spinal tracts
Called - cortico spinal tract (lateral), rubrospinal, reticulo spinal, vestibule spinal, tectospinal and cortico spinal (anterior)
Sensory
Dorsal column -
Broken down further into:
Fasciculus gracilis - carries info regarding lower limb
Fasciculus cuneatus - carries info regarding upper limb
As a whole the column relays info regarding:
Fine touch, 2 point discrimination, vibration conscious proprioception.
Sensory
Spinothalamic tract -
Relays info about:
Pain, course touch/pressure and temperature
Sensory
Spinocerebellar tract -
Responsible for unconscious proprioception and coordination
Motor
Corticopinal tract -
Responsible for our main voluntary/concious movement and control
Leaves spinal cord to produce motor output.
55% of fibres terminate in C spine
20% terminate in T spine
25% terminate L region
Therefore shows that upper limbs have a heavier weighting of control
Motor - extra pyramidal tracts, indirect pathways (do not cross)
Tectospinal -
Originates in mid brain, terminates cx spine
Response for auditory and visual stimuli = unconcious control of concious ability
Motor - extra pyramidal tracts - indirect pathways (do not cross)
Rubro spinal -
Originates in red nucleus (mid-brain)
Terminates mainly at cx spine
Role, tone - mainly flexors of the upper limbs. Unconcious control of conscious movement
Motor - extra pyramidal tracts, indirect pathways (do not cross)
Reticulospinal -
Originates in reticular formation in the brain stem (medulla)
Terminates at all levels of the spinal cord
Role - muscles tone, postural tone (axial)
Respiratory and circulatory systems
Unconcious control of conscious movement
Motor - extra pyramidal tracts, indirect pathways (do not cross)
Vestibulo spinal (lateral and medial) -
Originates vestibular nucleus in brain stem and terminates in the cx and thx regions
Role, extensor activity, balance and posture
Overview of the brain - where does it lie, what is it divided into:
Lies in the cranial cavity and is continuous with the spinal cord through the foreamen magnum (opening of base of skull)
Divided into four parts:
Brain stem - midbrain, pons and medulla
Cerebellum
Diencephalon - thalamus and hypothalamus
Cerebrum
Brain stem
1) mid brain -
Associated with vision, hearing, motor control, sleep and wakefulness, temp, alterness and regulation
Brain stem
2) pons -
Breathing and respiratory rhythm
Forms bridge between cerebrum and cerebellum (pons - Latin for bridge)
Brain stem
3) medulla oblongata-
Contains cardiac (hr,BP), respiratory, vomiting and vasomotor centres (deals with autonomic functions as well as the sleep-wake cycle)
Also where descending neurons (motor) cross to the opposing side
Role of Cerebellum -
Coordination of voluntary movements
Motor-learning
Balance
Emerging evidence in role in learning and attention
Contains more neurones than the rest of the brain combined
10% of total brain weight
Cerebellum - Latin for ‘little brain’
Diencephalon
Thalamus -
Principal relay station for sensory input
Sends signals to the sensory cortex
Diencephalon
Hypothalamus -
Regulated homeostasis though influence on autonomic system and pituitary gland
Structure of Cerebrum -
What is the corpus callosum?
Has two hemispheres
Left - controls right side of body
Right - controls left side of body
Divided by the longitudinal fissure
The surface of the brain covered by sulci (wrinkles)
Corpus callosum - bundle of fibres connecting two hemispheres which allows info to move between the two hemispheres
Structure of white and grey matter in the brain -
Outer layer of the brain is made up of grey matter
Central area is white matter with an area of central grey matter
Central grey matter - basal ganglia
Name the four lobes that make up the brain -
Each hemisphere is divided into four lobes
Frontal
Parietal
Temporal
Occipital
Role of the frontal lobe -
Main site of the ‘higher cognitive functions’
Voluntary movements
Attention
Personality
Emotion
Memory
Speech - Broca’s area
- left hemisphere for most individuals, expressive speech (thought translation to speech), sends impulses to motor cortex
Motor areas of the brain - frontal lobe
Primary motor cortex -
Responsible for initiation and control of movement
Sits behind the other two motor areas
Motor areas of the brain - frontal lobe
Pre motor area -
Functions are diverse and not fully understood yet
Direct control of behaviour with a relative emphasis on the trunk of muscles of the body
Plays a role in planning movement, in sensory guidance of movement
Motor areas of the brain - frontal lobe
Supplementary motor areas (SMA) -
Precise role if not known yet
Postural stabilisation of the body, coordination of both side of body
Control of movements that are internally generated rather than triggered by sensory events
Control of sequences of movement
Role of Parietal lobe -
Perception and integration of sensory information
Visuospatial procession
Spatial attention
Parietal lobe
Somatosensory cortex -
At front of parietal lobe
Receives sensory information from the thalamus
Sensory sensory info onto other areas in the brain
Located posterior to the primary motor cortex
Role of temporal lobe -
Perception
Face recognition
Object recognition
Memory acquisition
Language understanding (wernickes area)
Emotiona; reactions
Role of the occipital lobe -
Primary visual area of the brain (optic nerve connects)
Involved in the interpretation of visual input
- intensity of light and dark
- shape and movement of objects
- colour
What is the Basal ganglia -
Group of nuclei deep in the brain that regulate the initiation of movements, balance, eye movements and posture
Strongly connected to the other motor areas in the brain
Links the thalamus with the motor cortex
Involved in cognitive and emotional behaviours
Play an important role in reward and reinforcement, addictive behaviours and habit formation
Main neurotransmitter in this area is dopamine
What are the five main neculi in the basal ganglia -
Caudate nucleus
Globus pallidus
Putamen
Substantia nigra
Subthalamic nucleus
Role of the limbic system -
Important role in processing and regulating emotions, memories and sexual arousal
Important element in the bodies response to stress
Responsible for procession the bodies response to odours
Group of structures including:
Amygdala
Hippocampus
Hypothalamus
Cingulate gyrus
Meninges of the brain
Outer most layer -
3 layers of membrane cover the brain and spinal cord
Outer is closest to the skull called the dura matter
Tough, fibrous membrane that ensheathes the brain like a loose fitting bag
At floor of cranial cavity and midline of the cranial roof the dura is tightly adhered to the interior surface of the skull
Esleswhere to two are separated by a narrow extradural space
Meninges of the brain
The middle layer -
Called the arachnoid mater
Soft translucent membrane that loosely envelops the brain
Seperated from the dura mater by a narrow subdural space (through which veins pass)
Meninges of the brain
Inner layer -
Called the Pia matter
Most delicate layer
Microscopically thin delicate and highly vascular membrane that is closely adherent to the surface of the brain
Seperated from the arachnoid mater by the subarachnoid space
If there is damage to the parietal lobe you expect to see -
Damage to the frontal lobe you expect to see -
Damage to cerebellum you expect to see -
Parietal - sensory deficit
Frontal - behaviour, motor and expressive speech deficits
Cerebellum - coordination and balance problems
