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1

Branches of the nervous system

Central Nervous System (CNS)
Peripheral Nervous System (PNS)

2

Branches of the CNS and PNS

CNS
- Brain
- Spinal Cord

PNS
- Motor Neurons (from CNS to muscles and glands)
- Sensory Neurons (from sensory organs to CNS)

3

Branches of motor neurons

Somatic Nervous System
- voluntary movements

Autonomic Nervous System
- involuntary responses

4

Branches of the Autonomic Nervous system

Sympathetic Division
- Fight or Flight

Parasympathetic Division
- Rest or Digest

5

Anatomical Planes (5)

Medial Plane
Lateral Plane
Horizontal Plane
Coronal Plane
Sagittal Plane

6

Ipsilateral and Contralateral

Ipsilateral items lie on the same lateral side
Contralateral items lie of different sides of the body

7

Anatomical Relationships (spatial) (4)

Rostral = up (beak)
Caudal = down (tail)

Ventral (anterior) = belly
Dorsal (posterior) = back

These axes line up when you look up, so in normal anatomical position, for the head:
Dorsal = superior
Ventral = inferior

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Basic Divisions of the brain (3)

Forebrain
Midbrain
Hindbrain

9

10% of brain volume but 50% of the brain's cells

Cerebellum

10

Divisions of the Forebrain

- Telencephalon
> olfactory bulbs (for olfactory stimuli)
> cerebral hemispheres (regulation of sensory and motor function)

- Diencephalon (sensory gateway / regulation of internal environment)

11

Divisions of the Hindbrain

- Cerebellum
(movement coordination / learning of motor skills)

- Pons
(relay point between cerebellum and cerebral cortex in mammals)

- Medulla
(regulation of internal environment)

12

Divisions of the Midbrain

- Optic Tecta
(processing of sensory {mainly visual} stimuli)

- Tegmentum
(aspects of motor control)

13

Divisions of the cortex into lobes (forebrain)

Frontal Lobe
- motor control
- executive functions

Temporal Lobe
- hearing

Parietal Lobe
- bodily sensations
- spatial relationships

Occipital Lobe
- vision

14

Brodmann's areas

Divided the brain into areas according to structural divisions
However an apparent difference in structure does not mean a difference in function

15

Cranial Nerves

The structures that carry information into the brain
There are 12 cranial nerves in humans, the first 2 emerge from the cerebrum and the other 10 emerge from the brainstem

Cranial Nerves are part of the Peripheral Nervous System (sensory neurons)

16

Overview of brain functions:
- cerebral cortex
- basal ganglia
- thalamus, hypothalamus
- cerebellum
- pons and medulla
- midbrain

Cerebral cortex
- cognition
- sensory processing
- motor control
- learning

Basal Ganglia
- voluntary and learnt motion

Thalamus, Hypothalamus
- sensory integration and relay
- attention
- consciousness
- emotion
- homeostasis

Cerebellum
- motor coordination
- muscle tone and balance

Pons and Medulla
- involuntary body functions (i.e. sleep)
- cognitive motor skills (i.e. typing)

Midbrain
- audio/visual relay
- posture
- alertness

17

Ganglia

A group of related nuclei

18

Divisions of the spinal cord and what they innervate

8 Cervical nerves
- neck / shoulders / arms / hands

12 Thoracic nerves
- trunk of the body / arms

5 Lumbar nerves
- lower back / front of the legs

5 Sacral nerves
- back of legs + ass / genitals

19

Dorsal column-medial lemniscal pathway

Transmits sensory information but NOT pain
- from proprioceptors or mechanoreceptors

Pathway:
- Afferent (first-order) neuron from the receptor goes into the dorsal root ganglion of the spinal cord
- Passes up the Dorsal Column to the Medulla Oblongata, where it synapses onto a second-order
- 2nd order neuron travels out of the Dorsal Column and passes over the Medial-Lemniscus to the other side of the Medulla Oblongata and up into the Thalamus
- In the Thalamus, it synapses onto a third-order neuron and terminates in the Primary Somatosensory Cortex

20

Spinothalamic Tract (a pathway)

Transmits pain information
- from nociceptors or thermoreceptors

Pathway:
- Afferent neuron from the receptor goes into the dorsal root ganglion of the spinal cord
- Immediately synapses onto an interneuron in the dorsal horn and passes into the other side of the spinal cord
- This travels up to the thalamus where it synapses onto an efferent neuron and onto the Primary Somatosensory Cortex

21

What the dorsal column-medial lemniscal pathway and spinothalamic tract tell you about spinal damage

If damaged on one side of the spina cord:
- sensory information from below that same side will not travel up
- pain information from that opposite side will not travel up
- due to the way each pathway passes over to the other side of the spinal cord

22

Sympathetic vs Parasympathetic effects of the Autonomic Nervous System

Sympathetic
- dilates pupils and inhibits tears
- relaxes airways
- increases heart rate
- inhibits salivation and digestion / stimulates glucose release from the liver
- relaxes bladder and rectum
- stimulates orgasm
- stimulates release of adrenalin and noradranalin

Parasympathetic
- constricts pupils an stimulates tears
- constricts airways
- slows heart rate
- stimulates salivation and digestion / stimulates insulin release from the liver
- constricts bladder and rectum
- stimulates sexual arousal

23

Changes to the Autonomic Nervous system (by exercise and trauma)

Exercise
- recreational athletes show a shift towards the sympathetic nervous system
> if persistent this can cause high blood pressure and cardiovascular disease
- long term intensive athletic training causes a shift towards the parasympathetic nervous system

Trauma
- PTSD causes a heightened sensitivity in the autonomic nervous system
- tends to have persisting effects

24

Brain facts

- Brain is 2% of the body mass but receives 15% of the body's blood supply and receives 20% of the body's oxygen
- no brain cell is further than 50 um (micrometers)

25

Meninges

Dura mater
- tough and inflexible, divided into several layers

Arachnoid mater
- delicate, impermeable and avascular

Pia mater
- adheres closely to the brain
- fuses with the lining of the ventricles to form structures that produce cerebrospinal fluid (CSF)


The Peripheral Nervous System (PNS) has no pia mater, only 2 layers

26

CSF

Produced mainly by the Choroid Plexus, about 500ml daily

27

Homology

Structures can be considered as homologous if they have similar:
- structure
- connections
- chemical signalling
- gene expression
- function

28

Three R's in animal research

All research should aim to:
- Reduce the total number of animals used
- Replace live animal testing with anything else where possible
- Refinement (minimise suffering and distress to the animal)

29

Development of the body from 3 plates

Ectoderm
- forms the skin and nervous system

Mesoderm
- forms bones and muscles

Endoderm
- forms the lining of internal organs

30

Development of the Ectoderm

- After 22 days from gestation, the neural plate forms the neural tube via Neurulation:
> Neural plate folds at the Neural plate borders, forming a Neural Groove
> When the Neural Folds fuse together, this groove becomes the Neural Tube and the folds form the Neural Crest
+ The Central Nervous System develops from the Neural Tube
+ The Peripheral Nervous System develops from the Neural Crest

31

Birth defects of nervous system maldevelopment (spina bifida)

Spina Bifida
- the most common birth defect associated with live birth
- occurs when the neural groove doesn't properly close up to form the neural groove, so there is a gap

Severities:
- Occulta
> asymptomatic, normally a tuft of hair at the location
- Meningocele
> a sack containing spinal fluid at the location of non-fusing
- Myelomeningocele (80-90% of cases)
> a sack containing spinal cord, nerves and spinal fluid

Symptoms:
- depend on the severity and location
- High on the spine could cause paralysis
- Lower down could cause incontinence

- Movement problems:
> weakness or paralysis of lower limbs
> deformed bones
- Bladder and bowel problems
> incontinence / UTI
- Associated Hydrocephalus (enlarged head) [least common]
> with many associated learning difficulties

32

Risk factors for Spina Bifida

- being white
- being a girl
- the mother has diabetes
- the mother is obese
- the mother has a folate (folic acid / vitamin B6) deficiency
- certain medications (i.e. anti-seizure)

33

Differentiation of the Neural Tube

- firstly into 3 Primary Brain Vesicles
> Forebrain, Midbrain, Hindbrain
> Prosencephalon, Mesencephalon, Rhombencephalon
- then these further differentiate:
> Forebrain differentiates into 2 Telencephalic Vesicles, 2 Optic Vesicles and the Diencephalon
> Midbrain differentiates into the Mesencephalon, which differentiates into the Tectum, Aqueduct and Tegmentum which form a layered tube (around the Cerebral Aqueduct)
> Hindbrain differentiates into the Cerebellum, Pons and Medulla (also the 4th ventricle which is continuous with the aqueduct)