14/10/20151 control systems central nervous system (brain and spinal cord)
TRANSCRIPT
21/04/23 1
Control Systems
Central Nervous System(Brain and Spinal Cord)
21/04/23 [email protected]
AIMS
• To provide learners with an overview of the principal anatomy and related physiology of the central nervous system – the brain and the spinal cord.
BRAIN + SPINAL CORD
21/04/23 [email protected] 3
Outcomes
Learners will be able to describe:
the principal anatomy and related physiology of the central nervous system – the brain and the spinal cord.
Microsoft clip art
21/04/23 [email protected] 4
Brain functions
Keeps the basic, body functions such as heart beat rate, breathing rate and temperature control ticking over, without us having to think about it.
It also allows us to decide to do things like running and walking and many more complex tasks. It is where our personalities and moods and emotions come from.
Microsoft clip art
21/04/23 [email protected] 5
Brain Overview Makes up about one-fiftieth of the body's
weight
Protected by the skull and by membranes called the meninges.
(Think of meningitis - the illness that results from an infection of the meninges).
Cerebrospinal fluid bathes the outside of the brain and fills the ventricles. - PROTECTIVE
The brain receives signals from inside and outside the body. RECEPTIVE
The human brain is thought to contain ten billion (1010) neurones - about the same number as the stars in our Galaxy. – IMMENCE POTENTIAL
Each neurone may be in contact with a thousand other cells, providing an immense number of different communication routes. -VAST COMMUNICATION ABILITY
Microsoft clip art
21/04/23 6
Brain Lobes- Functions (1)
The brain is divided
anatomically into
3 main structures: 1. The cerebrum.
1. Frontal Lobe2. Parietal Lobe3. Temporal Lobe4. Occipital Lobe
2. The cerebellum.
3. The brainstem.
Functions: e.g.Hearing- Wernicke’s area - AuditorySpeech – Broca’s area
21/04/23 7
Cerebral Cortex – uppermost part of the
hemispheres
(Cortex means "bark" in Latin.) [ Grey Matter] 2/3rd of the brain.
(unmyelinated neurones process motor and sensory functions- communicate with cortical areas. Also with other brain areas via underlying myelinated fibres (white matter)
This surface is made up of gyri and sulci- Lumps and grooves
(surface area.)
.
http://en.wikipedia.org/wiki/Cerebral_cortexAccessed 25/10/12
21/04/23 8
A fold in the Dura
mater
Albert Kok at http://en.wikipedia.org/wiki/File:Gyrus_sulcus.png (24/10/12)
Depressions and Furrows
Right and left HemisphereCommunication
http://serendip.brynmawr.edu/bb/kinser/Size1.html
Compare relative size re smooth appearance of squirrel brain v gyri and
sulci of human brain
Ventricles of the Brain
Filled with cerebrospinal fluid (CSF)- bathes and cushions brain /spinal cordCSF is produced in the choroid plexus (CP).
The CP is made up of capillaries, separated from the ventricles by specialised epithelial cells. Plasma filters through these cells from blood to become cerebrospinal fluid. Active transport takes substances in and out of the newly formed CS.
CP epithelial layer has tight junctions in between the cells on the side facing the ventricle).
Tight junctions prevent the majority of substances from crossing the cells to enter the CSF
The CP acts as a blood-CSF barrier. The CSF flows from the ventricles to the subarachnoid space to bathe the brain and the spinal cord
Marieb 12.5 Copyright 2006 Pearson Education . Inc,. Publishing as
Benjamin Cummings
Image: © Nevit Dilmen found at Wikimedia commons Accessed 25/10/12
If this blocks hydrocephalus can occur
21/04/23 [email protected] 10
Cerebral Cortex: The Thinker thinking and learning creativity five senses memory and emotion problem-solving decisions
The cerebral cortex is the largest part of the brain.
It does a lot of brain work, like thinking, decisions, and creativity.
It's the part of the brain that allows you to think about who you are.
21/04/23 11
The Cerebrum.• Difference in the relative size of
hemispheres and connection between them (corpus callosum) can produce substantial individual differences and such is thought to relate to behavioural attributes including sexual identity. (see research articles)
• The left side of the brain has been shown to control the right side of the body; spoken and written language and scientific, reasoning and numerical skills.
• The right side is more concerned with emotion and artistic and creative skills.
21/04/23 12
Right Cerebral Hemisphereassociated with
• Holistic processing of multi-sensory input
• Visual spatial skills
• Memory stored in auditory, visual, & spatial modes
• Remembering non-verbal material
• Colour discrimination
21/04/23 13
Left Cerebral Hemisphere – associated with
• Analytic & sequential thinking
• Language
• Mathematics
• Abstraction & reasoning
• Ability to name objects & their attributes
• Memory stored in language format
21/04/23 14
21/04/23 15
The Corpus Callosum
In severe epilepsy severing the corpus callosum can stop the speed of epileptic seizures from one hemisphere to the other
Research considers individual differences in the size and shape of the corpus callosum that may relate to sexual identity and consistency of right or left handedness .
Results are very vague
Years ago the corpus callosum was surgically interfered with to try to
treat mental illness?
An important connection between the two halves of the brain. It mediates communication between the two hemispheres of the brain.
21/04/23 [email protected] 16
The CerebellumHas two hemispheres
Each is divided into lobes, and is covered by the cortex.
It is very important for the production of speech.
It organizes muscle activity and plays a role in the coordination of fine motor movements and also in balance.
The cerebellum receives both motor and sensory input, and so is the centre of a feedback loop.
21/04/23 [email protected] 17
The CerebellumMotor messages that leave the brain also go to the
cerebellum, including information about the strength of the impulses.
It integrates motor output so that movements are smooth and coordinated.
It is connected to the brain stem by three pairs of tracts called the cerebellar peduncles.
Muscle spindles, joints and tendons send information about movement back to this area. The cerebellum then relays these messages to the cortex, completing the feedback loop.
Cerebellar trauma will cause which involves jerky, uncoordinated movements of the speech musculature (ataxic dysarthria )
21/04/23 18
The Basal GangliaAn area of grey matter within each cerebral hemisphere
The basal ganglia are a collection of motor nucleii which help to coordinate muscle movements by relaying information via the thalamus to the motor cortex.
Assists in the control of body movements etc.
CLINCIAL RELEVANCE POINT: Parkinson’s Disease, ADHD, cerebral palsy, dytonias, obsessive compulsive disorder etc. are associated with the basal ganglia problems
Leevanjackson ransfered from en.wikipediaAccessed 25/10/2012)
21/04/23 19
The Thalamus • TWO large egg shaped
masses – one in each hemisphere.
• Divided into nucleii, which are major relay stations for information going to and from the cerebral cortex.
• All sensory pathways have direct projections to thalamic nuclei which convey information to particular areas of the cerebral cortex.
• Communicates with Limbic system- see later
The Amygdala Stores emotional memory.
Involved in the sense of smell- certainly associated with sense of danger
Sends impulses to the mid brain and brain stem:
Results in release of adrenaline and noradrenaline = Stress hormones 21/04/23 20
Creative Commons CC0 1.0 Universal Public Domain Dedication http://en.wikipedia.org/wiki/Amygdala accessed 31/10/12
Hippocampus
Involved in spatial navigation
Consolidates information from short-term to long-term memory.
Clinical relevance point: Think of Alzheimer's disease and the disorientation and loss of memory that occurs when this structure is damaged.
21/04/23 21
Creative Commons CC0 1.0 Universal Public Domain Dedication http://en.wikipedia.org/wiki/Amygdala accessed 31/10/12
21/04/23 22
Hypothalamus + homeostasis
Below and partly in front of the thalamus.
Connects the cortex to basal ganglia, thalamus, midbrain, pons, medulla and spinal cord
Regulates the functioning of the pituitary gland, controlling: Autonomic nervous function
Major endocrine effectse.g. water balanceappetitesex drive,
.
21/04/23 [email protected] 23
Thalamus/ Hypothalamus
The Thalamus is an input structure, sending messages to higher brain areas,
The Hypothalamus is an output structure, sending messages to other parts of the brain and endocrine glands.
21/04/23 [email protected] 24
The Midbrain and reticular activating system.
Contained within the midbrain and upper pons is the reticular activating system.
This is responsible for the ‘awake’ state & arousal from sleep or altered level of consciousness.
Image used with permission
enhancingmylife.blogspot.com,
21/04/23 25
The Reticular Formation
In addition perception of sensory information this determines which parts of the constant flow of sensory information from the body conveyed to the cerebrum.
Image used with permission
enhancingmylife.blogspot.com,
21/04/23 [email protected] 26
The PonsConnects the brain stem to the cerebellum. A relay station from the medulla to higher structures found in the brain.
Functionsrespiratory centre – contributes to control of respiration
trigemenal nerve (V)--facial skin, tongue, teeth, mastication (chewing)
abducens nerve (VI) controls muscle that rotates eye outward
facial nerve (VII) controls muscles of expression
acoustic nerve (VIII) hearing & balance
MedullaThe lower half of the brainstem.
Contains the cardiac, respiratory,
vomiting and vasomotor centres.
Action: Autonomic, involuntary, e.g.
Breathing- e.g. signals to breath = H+ plasma concentration - activates respiratory centres – muscles stimulated to increase depth and rate in respiration
Heart rate and Blood pressure - e.g signals to increase heart rate and vasoconstriction = baroreceptor activation -vasomotor centre- sympathetic drive.
All cranial nerves (12) except the olfactory and optic (as they are going forward to front of head) emerge from the brainstem
21/04/23 27
Limbic systemThis consists of the hypothalamus, cingulated gyrus, amygdala, hippocampus, mamillary bodies and septum
Influences endocrine and autonomic nervous systems
Connected with the brain's pleasure centre (nucleus accumbens) – sexual arousal and the "high" from recreational drugs. (emotion and memory)
Connected to prefrontal cortex- related to the
pleasure obtained from solving problems etc.
21/04/2328
By lecerveau.mcgill.ca [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons accessed 30/10/2012
The brain and pregnancy
Stimulation of specific areas of this system can also lead to feelings of dread, high anxiety, It can also result in violent behaviours, (attack, defence , explosive and emotional speech) (ANGER).
Supporting Cells
21/04/23 29
Microglia are extremely sensitive scavenging cells of the CNS. They look for damaged neurons and infectious agents.
Oligodendrocytes: Glial cells which wrap their cytoplasmic extensions around the nerve fibres – forming a covering called the MYELIN SHEATH - within the Central Nervous System.
Astrocytes are star shaped Macroglial cells within the brain and spinal cord. They cling to blood vessel sand neurones.= the most abundant glial cells within the brain and they serve to regulate electoral transmission and they perform immune functions They provide energy to neurones (taking glucose from serum changing this to lactate for neurons to use as fuel) .
Schwann Cells for the myelin sheath within the PNS
Nathan S. Ivey and Andrew G. MacLean (2009) Neurorocker at en.wikipedia accessed 25/10/12
© UWCM/SONMS/Pain/MJohn
Myelinated and Unmyelinated Fibres
21/04/2331
The Spinal CordStarts at the base of the brain and ends at the 1st or 2nd lumbar vertebrae.
The bony cage of the vertebral column and has an internal core - diameter of about five millimetres.
Cord protection is then provided by three layers of the spinal meninges with CSF to cushion the cord.
Marieb 12.31a Copyright 2006 Pearson Education . Inc,. Publishing as Benjamin Cummings
21/04/23 [email protected] 32
The Spinal Cord and PNSEach vertebra has an opening on its
right and left sides to let spinal nerves pass through.
These extend into the body, forming the peripheral nervous system.)
Function
1. Acts as a relay station between the peripheral nerves .and the brain
2. Act as an activating centre, taking incoming sensory impulses and initiating outgoing motor signal.
3. Coordinates reflexes
Marieb 12.29a Copyright 2006 Pearson Education . Inc,. Publishing as Benjamin Cummings
21/04/23 [email protected] 33
33 Spinal vertebrae and 31 Spinal nerves
Vertebra- Nerves
7 Cervical- 8
12 Thoracic-12
5 Lumbar- 5
5 Sacral- 5
4 Coccyx- 1(fused vertebrae)
Martini 13-11
Spinal nerves originate from the spinal cord
The Spinal cord
Consists of 31 pairs of spinal nerves that arise form the spinal cord and 12 pairs of cranial nerves that arise from the brain stem.
Spinal cord CNS
21/04/23 [email protected] 34
21/04/2335
Spinal Cord functions
1. Acts as a relay station between the peripheral nerves and the brain.
Consists of two layers : white matter – myelinated axons (outer layer) and grey matter - neurons and synapses (inner layer)
Marieb 12.31b Copyright 2006 Pearson Education . Inc,. Publishing as Benjamin Cummings
21/04/2336
Spinal Cord functions 12. Acts as an activating centre, taking incoming sensory impulses and initiating outgoing motor signals i.e. ‘a reflex arc’
Marieb 13.14
21/04/23 37
‘H’ Shape divided into three functional parts
The Posterior (Dorsal) horns carry SENSORY IMPULSES
The middle zone undertakes associated functions between the Posterior and Anterior horns on the same and opposite side of the ‘H’ shape .
The Anterior (Ventral ) horns carry MOTOR IMPULSES
Ventral (anterior) = front of body
Marieb 12.32 Copyright 2006 Pearson Education . Inc,. Publishing as Benjamin Cummings
Dorsal (posterior) = back of body
21/04/23 [email protected] 38
Spinal Nerve Basics Each has two roots connecting to the spinal cord: The posterior (dorsal) is the sensory root;The anterior (ventral) is the motor root. The peripheral nervous system is outside the spinal cord
Peripheral Sensory receptors send information from the body to the posterior route ganglion of the spinal cord (and then to the brain).
Some fibres synapse with other neurons (inter or association neurons) in the posterior horn, while others continue up to the brain. Nerve cell bodies in the ventral / anterior horn send Motor signals to muscles via their axons through the ventral / anterior root to control movement.
© UWCM/SONMS/Pain/MJohn
Sensory Pathways to and from the Brain
© UWCM/SONMS/Pain/MJohn
Spinothalamic Tract
21/04/23 41
Ascending and Descending Spinal Nerves
Spinothalamic tract, Carries pain and temperature impulses to the thalamus and the parietal lobe
Posterior columns, carrying position and pressure sense to the thalamus and the parietal lobe
Corticospinal, carrying impulses to initiate muscle activity from the frontal lobe.
Peripheral Receptors
Examples: Mechanoreceptors - hearing and balance, stretching
Thermoreceptors - temperature
Photoreceptors – light
Electrorecpeptos – electrical current
Chemoreceptors – taste smell, internal chemical consistency
© UWCM/SONMS/Pain/MJohn
Example of a Sensory Neurone
21/04/23 [email protected] 44
© UWCM/SONMS/Pain/MJohn
Endoneurium of axon
© UWCM/SONMS/Pain/MJohn
Saltatory Conduction recap
Neurotransmitters Examples of Major Types
Amino acids: glutamate,[ γ-aminobutyric acid (GABA), glycine
Monoamines : dopamine, adrenaline, noradrenaline histamine, serotonin.
Peptides: somatostatin, substance P, opioid peptides
Others: acetylcholine (ACh), adenosine, oxytocin, nitric oxide, etc.
21/04/2347
Axon terminal
Synaptic cleft
Receptor
Vesicle carrying neurotransmitter
Neurotransmitter
Dendrite of the nerve body
Neurotransmitter substance diffuses across the synaptic cleft
© UWCM/SONMS/Pain/MJohn
21/04/[email protected]
49
Reflexes An automatic, i.e."involuntary," response of the body to some stimulus, e.g. pupil dilation, to collect more light, at night.
Reflexes have afferent (signals to the CNS) and efferent (signals from the CNS) components and may involve one nerve / synapse (monosynaptic reflex) or multiple synapses (polysynaptic reflex).
The simplest spinal reflex is the tendon reflex, a monosynaptic reflex.
The tendon is tapped-
Sensory receptor in the muscle sends a signal to the spinal cord (afferent system), via the dorsal/posterior root,
then synapses with a sensory nerve axon in the ventral/anterior horn.
The receiving axon carries the impulse through the ventral/anterior root back to the muscle (efferent system) -The muscle jerks/ contracts.
21/04/23 [email protected] 50
21/04/23 [email protected] 51