9. Nervous System Organisation Flashcards
1
Q
CNS is..
A
Central Nervous System - brain and spinal cord
2
Q
PNS is..
A
Peripheral Nervous system - nerve fibres that carry information between the CNS and other parts of the body
3
Q
Afferent vs. Efferent
A
Afferent - inwards towards CNS
Efferent - e.g. motor command
4
Q
Sensory vs. Visceral stimuli
A
Related to Afferent division
Sensory - touch, see, smell etc
Visceral - input from organ sensors
5
Q
Efferent Division
A
- splits into somatic and autonomic nervous system
somatic: Voluntary motor movement e.g. move my arms, skeletal muscles (aware/conscious)
autonomic: sympathetic and parasympathetic nervous system, rest of muscle types (not consciously controlling)
6
Q
What is this
A
CNS and PNS overview
7
Q
3 functional classes of neurons
A
- afferent neuron - starts in PNS, end in CNS
- efferent neuron - start in CNS, end in PNS
- interneurons - starts and end in CNS - (can connect afferent neuron and efferent neurons and interneurons mainly found in brain)
8
Q
Structure and function of CNS
A
Brain and spinal cord
cognition referee to the act or process of ‘knowing’ including awareness and judgement
no part of the brain works in isolation
9
Q
Brain diagram
A
Core vital life functions in centre of brain
Thought processes and thinking in cerebral or outer brain layer
10
Q
Major brain functions
A
11
Q
Protection of the CNS
A
Glial Cells - support cells (90% if cells within CNS, called neuroglia cells)
- don’t conduct nerve impulses
Astrocytes - most abundant glial cell and fills a number of critical functions
Microglia - immune cells of the CNS
Ependymal - line cavities and contribute formation of CSF (cerebral spinal fluid)
12
Q
Protection of CNS diagram
A
Note oligodendrocyte are…
13
Q
Blood brain barrier
A
- Shields brain from harmful changes in the blood
- Consists of endothelial cells
- Tight junctions prevent exchange across the capillary wall
- Lipid soluble substances such as oxygen and alcohol can penetrate cells
- ie if not lipid soluble needs a carrier protein
14
Q
Role of Oxygen and Glucose
A
- Brain is highly dependent on constant blood supply
- Brain can not produce ATP in absence of oxygen
- Brain does not store glucose
- Damage occurs if oxygen is cut off for 5 mins or glucose for more than 15 mins
15
Q
Cerebral Cortex
A
- largest portion of the brain
- Two halves (right and left cerebral hemispheres joined by corpus callosum)
- Corpus callosum allows two hemispheres to communicate and cooperate with each other
16
Q
Brain picture
A
2 halves
note: corpus callosum is in middle
17
Q
Cerebal Cortex colour
A
- Thin outer shell of grey matter (neuronal cell bodies) on each hemisphere - densely packaged
- Bundles or tracts of myelinated nerve fibres (axons) constitute the white matter - Transmit signals from one part of the cerebral cortex to another and to other regions of the CNS
18
Q
Outer brain diagram
A
19
Q
A
20
Q
A
Motor Homunculus
(and left side brain, left side body)
21
Q
Plasticity and Neurogenesis
A
- ability to change or be functionally remodelled in response to the demands
- when an area of the brain is destroyed other areas of the brain may gradually assume some or all of the functions of the damaged region
22
Q
A
Sensory Input to Motor output example
- going from low level/sensitivity data to higher level choices in brain
23
Q
Cerebral Hemispheres
A
left side is commonly dominant hemisphere for fine motor control, so most people are right handed
left side excels in logical, analytic, sequential & verbal tasks
right side excels in nonlanguage skills such as spatial perception, arts & music
24
Q
Basal Ganglia
A
consist of several masses of grey matter located deep within the cerebral white matter
– Complex role in movement
25
Thalamus
deep in brain near the basal ganglia
* serves as a relay station and integrating centre
26
Hypothalamus
is an integrating centre that lies beneath the thalamus
* multifunctional regulating the internal environment
27
Limbic System
surrounds brain stem and not a separate structure
an interconnected ring of forebrain structures
related to
* emotions - amygdala
* basic behavioural patterns
* reward and punishment centres
28
Brain stem
* pons
* medulla oblongata
* midbrain
29
5 functions of the brain stem
**Five Functions of the Brain Stem**
Majority of cranial nerves arise from the brain stem
Contains centers that control cardiovascular, respiratory, and digestive function
Regulates postural muscle reflexes
Reticular activating system (RAS): controls the
overall degree of cortical alertness
Plays a role in the sleep–wake cycle
30
Spinal cord
* spinal cord extends from brain stem
* paired spinal nerves emerge from the spinal cord through spaces in vertebrae
* thick bundle of elongate nerve roots within the lower vertebral canal is called the caudal equina - like a horse's tail
31
**Organization of Neural Tissue in the Spinal Cord**
opposite in spinal cord
**Spinal Cord White Matter**
– Organised into tracts (ascending and descending tracts)
– Located in the outer section of the spinal cord
**Spinal Cord Grey Matter**
* Dorsal (posterior) horn - receiving sensory input (afferent neurons)
* Ventral (anterior) horn - motor input (with efferent neurons)
* Lateral horn - autonomic processes
* Located in inner section of the spinal cord
32
Spinal Nerves
* Spinal nerves connect with each side of the spinal cord by a dorsal root and a ventral root
* A spinal nerve consists of both afferent and efferent fibres
* A nerve is a bundle of peripheral neuronal axons enclosed by a connective tissue covering and following the same pathway
* the arms will be higher on the spine compared to the legs for example
33
Levels in the spinal cord
* cervical nerves - neck
* thoracic nerves - upper body
* lumbar nerves - lower back, pelvis, legs
* sacral - urinary tract
* coccygeal nerve
34
The PNS (**Peripheral Nervous System)**
The PNS consists of nerve fibres that carry information between the CNS and other parts of the body
**Afferent division** of the PNS: Sends information from internal and external environment to CNS (i.e. carries signals *to* CNS).
**Efferent division** of the PNS: Communication link by which CNS controls activities of muscles and glands (i.e. carries signals *from* CNS).
35
* Nerve, bundle of nerve fibres, called fascicles bundles with other fascicles and connective tissue
* As it moves further from spinal cord it branches off and splits into single nerves
36
Afferent Division - towards central nervous system
* **Visceral afferent**
* Incoming pathway for information from internal viscera (organs in body cavities)
* **Sensory afferent**
* somatic (body sense) sensation - arising from body surface and proprioception and where you are in space/touch
* Special senses - vision, hearing, taste, smell
37
Receptor Physiology
Structures (receptors) at peripheral endings of afferent neurons
Detect stimuli (change detectable by the body e.g. temperature)
Convert forms of energy into electrical signals (action potentials)
– Process is called transduction
38
Types of Receptors
**Photoreceptors** - responsive to visible wavelengths of light
**Mechanoreceptors** - sensitive to mechanical energy (pressure, stretch, vibration)
**Thermoreceptors** - sensitive to temp/hot & cold
**Osmoreceptors** - detect changes in concentration of solutes in body fluid and resultant changes in osmotic activity
**Chemoreceptors** - sensitive to specific chemicals, & include receptors for smell and taste and receptors that detect O2 and CO2 concentrations in blood and chemical content of digestive tract
39
**Stimuli and Receptor Permeability**
Receptors may be either
– The **specialized ending** of an afferent neuron
– a **separate cell** closely associated with peripheral ending of a neuron
* • Stimulus alters **receptor’s permeability**, which leads to **graded receptor potential \> then reach a threshold and cause an _action potential_**
* nonselective opening of all small ion channels – This change in membrane permeability can lead to the influx of sodium ions
* This produces receptor (generator) potentials
The magnitude of the receptor potential represents the intensity of the stimulus - a receptor potential of sufficient magnitude can produce an action potential.
This action potential is propagated along an afferent fibre to the CNS
40
Types of receptors and speed of adaptation
* receptors may adapt slowly or rapidly to sustained stimulation
* tonic receptor - do not adapt or slowly e.g. muscle stretch receptors, joint proprioceptors
* phasic receptor - rapidly adapting e.g. tactile receptors in skin
41
**Efferent Division**
Autonomic nervous system (ANS)
– Involuntary branch of PNS
– Innervates cardiac muscle, smooth muscle, most exocrine glands, some endocrine glands, and adipose tissue
Somatic nervous system
– Subject to voluntary control
– Innervates skeletal muscle
42
Autonomic Nervous System
* sympathetic nervous system - fight or flight, emergency or stress
* promotes responses that prepare body for physical activity
* parasympathetic nervous system – quiet and relaxed situations
* promotes body-maintence activities such as digestion
43
Effects of autonomic nervous system on various organs
44
Somatic Nervous system
Consists of axons of motor neurons **from** spinal cord or brain stem and **end** on skeletal muscle
Motor neurons are the final common pathway by which various regions of CNS exert control over skeletal muscle activity - areas of CNS include spinal cord, motor regions of cortex, basal nuclei, cerebellum, and brain stem
