Nervous system - structure and development

Question 1

In four legged animals what does dorsal: ventral mean?

Answer 1

Back and belly

Question 2

what does Cranial: caudal mean?

Answer 2

Head end and tail end

Question 3

What does proximal: distal mean?

Answer 3

Close to and far away

Question 4

In four legged animals what does anterior: posterior mean?

Answer 4

front end and back end

- in a four-legged animal it means the same thing as cranial: caudal

Question 5

What does rostral mean?

Answer 5

Nose or mouth end

Question 6

What does Medial: lateral mean?

Answer 6

Towards the midline or away from it

Question 7

What does anterior: posterior mean in two legged animals?

Answer 7

The same as ventral and dorsal: belly and back

Question 8

What does superior: inferior mean in two legged animals?

Answer 8

position in the vertical axis - closer to head or feet

Question 9

What does cephalic: caudal mean?

Answer 9

Head: tail end (cephalic is sometimes used instead of cranial)

Question 10

What is the frontal plane?

Answer 10

Sliced from the front

Question 11

What is the sagittal plane?

Answer 11

Cut into left and right

Question 12

What is the transverse plane?

Answer 12

Cut horizontally

Question 13

What are motor/ efferent neurones?

Answer 13

Neurones that carry a signal towards a target tissue or organ, in order to make something happen

Question 14

What are sensory/ afferent neurones?

Answer 14

Sensory neurones detect changes in the environment and carry signals about that change to the central nervous system

Question 15

What does the autonomic nervous system do?

Answer 15

The autonomic nervous system (ANS) controls many of our bodies’ involuntary responses to its environment. It is divided into the sympathetic nervous system and the parasympathetic nervous system.

Question 16

What is one of the reasons we have a nervous system?

Answer 16

So we can move

Question 17

What do sponges, jellyfish (invertebrates) ect. have instead of a nervous system?

Answer 17

A nerve net

Question 18

What do more advanced invertebrates (arthropods) have as their nervous system?

Answer 18

• ventral cord (compared with dorsal cord in vertebrates)

- brain

Question 19

When did the vertebrate brain appear?

Answer 19

• Small collection of neuronal control circuits (primitive brain) in amphioxus (cephalochordate)
• Higher in the evolutionary change we can see a brain with brain divisions common to all vertebrates (e.g. a shark brain): olfactory bulb, cerebral hemispheres, cerebellum, optic tectum, brain stem containing medulla oblongata
• Mammals: neocortex (enables us to process complex information)

Question 20

What four sections is the central nervous system of vertebrates split up into?

Answer 20

• forebrain
• midbrain (part of brain stem)
• hindbrain/ rhombencephalon (part of brain stem)
• spinal cord

Question 21

What does the forebrain contain?

Answer 21

 Telencephalon: cortex and olfactory bulb

 Diencephalon: thalamus and hypothalamus

Question 22

What does the midbrain contain?

Answer 22

 Mesencephalon: tectum and tegmentum

Question 23

What does the hindbrain contain?

Answer 23

 Pons
 Medulla
 Cerebellum (separate from brain stem)

Question 24

What are the three layers of cells in an embryo?

Answer 24

 Endoderm (linings of organs; viscera)
 Mesoderm (bones and muscles)
 Ectoderm (nervous system and skin)

Question 25

How does the nervous system develop?

Answer 25

- first the ectoderm starts to become specialised - a streak forms down the middle - Specialisation in the neural plate - a region which is going to become the nervous system - Specialisation in a region which is going to become the epidermis (there is a neural plate border between these two regions) - The middle of the neural plate starts to dip down – the neural plate folds and fuses to form the neural tube (continuous layer of epidermis with neural tube and neural crest beneath it) - CNS develops from the walls of the neural tube. PNS (peripheral nervous system) derives from the neural crest - The notochord arises from the mesosome and will eventually develop into the vertebral column, it helps with the orchestration of the changes that the neural tube undergoes - As the neural tube closes it zips up from the middle and the closing carries on to the anterial and posterial end, you end up with a pore at each end which need to close

Question 26

What happens if the anterial pore of the neural tube doesn't close and what is this called?

Answer 26

- the brain won't develop | - anencephaly

Question 27

What happens if the posterior neural tube doesn't close and what is this called?

Answer 27

- there is a gap in the vertebral column and portion of spinal cord poking out of the baby’s back - called Spina bifida

Question 28

What is important in the closure of pores and what may interfere with this?

Answer 28

- folic acid | - some anti epilepsy/bipolar drugs interfere with folate metabolism and increase risk of Spinal bifida

Question 29

What happens in a 3-4 week embryo in regards to the neural tube?

Answer 29

there are three swellings at the rostral end of the neural tube becoming the primary vesicles – the forebrain, midbrain and hindbrain

Question 30

What ventricles do we have in the brain, where are they located and what are the filled with?

Answer 30

- Ventricles contain CSF (cerebrospinal fluid) - We have four ventricles - Two lateral ventricles - Third ventricle in the centre - Fourth ventricle at the bottom

Question 31

How are the ventricles in the brain connected?

Answer 31

Ventricles connected by canals – interventricular foramen, cerebral aqueduct and central canal which extends down to the brain stem (which is also hollow and fluid filled)

Question 32

What is the spinal cord protected and surrounded by?

Answer 32

Protected by spinal column, surrounded by meninges and cerebrospinal fluid (CSF)

Question 33

What does the spinal cord do?

Answer 33

It is the primary channel for messages from skin, joints and muscles to brain and from brain to periphery

Question 34

What do the dorsal roots of the spinal cord contain and how are they arranged?

Answer 34

- sensory, afferent neurones - there is a collection of fibres from sensory neurones – the cell bodies are located in the dorsal root ganglion. They have an single process an axon which splits into two – one bit goes to the periphery where it picks up the information and the other part goes into the spinal cord

Question 35

What do the ventral roots of the spinal cord contain and how are they arranged?

Answer 35

- motor, efferent neurones - The ventral root contains motor neurones which leave the spinal cord through the ventral root and the join the neurones of the dorsal root to form a nerve

Question 36

What is a nerve?

Answer 36

A bundle of nerve fibres

Question 37

What shape can you see in the spinal cord and why?

Answer 37

you see a butterfly shape made of grey matter (neuron cell bodies). Surrounding this you see white matter (myelinated axons)

Question 38

What does the brain stem do and what does it contain?

Answer 38

- Oldest part of the brain – decision matrix. Controls vital functions - Contains:  Midbrain – movement, sensory input: eyes, ears  Hindbrain – pons, medulla

Question 39

Where are the pons and medulla located?

Answer 39

At the base of the brain

Question 40

What does the pons do?

Answer 40

swells out from ventral surface of brain stem. Important relay between cortex and cerebellum

Question 41

What does the medulla do?

Answer 41

Important in control of blood pressure and respiration (important in autonomic nervous system)

Question 42

What happens with brain stem damage?

Answer 42

- Either due to a direct injury to the brain stem or an injury to somewhere else in the brain: - Hydrocephalus or haemorrhage – build up of fluid in the skull from an injury to somewhere else in the brain.  Fluid will lead brain to be pushed downwards and the brain stem will be pushed down through the spinal cord hole leads to coning - Severe cases can lead to ‘coning’. Damage to the medulla causes respiratory arrest

Question 43

What is the cerebellum and what does it do?

Answer 43

- An ‘old’ part of the brain - Movement control centre - Extensive connections to cerebrum and spinal cord. Contains at least as many neurons as both cerebral hemispheres

Question 44

Why does alcohol produce movement problems?

Answer 44

because there are particular receptors in the cerebellum which are very sensitive to alcohol

Question 45

Give an example of a disease of the cerebellum

Answer 45

ataxias – aberrant movement coordination (seems like you are drunk)

Question 46

What is it called if someone doesn't have a cerebellum?

Answer 46

Cerebellum agenesis

Question 47

Where is the Thalmus and what does it do?

Answer 47

Located at the centre of the brain. Controls input to the cortex

Question 48

Give features of the cerebral cortex (cerebrum)

Answer 48

• Newest part of the brain in terms of evolution • Clear division between two halves along sagittal fissure • The bigger the cortex compared to it’s body size is related to it’s cognitive abilities (larger cerebral cortex -> larger cognitive ability) - number of neurons related to 'intelligence'

Question 49

What does the cerebral cortex control?

Answer 49

- Voluntary actions - Cognition - Perception/ awareness

Question 50

What is the difference between the cortex in mammals and reptiles and birds?

Answer 50

* Mammals have a more complex 6-layer structure of the cortex = neocortex * Reptiles and bird only have 3 layers

Question 51

What is the neocortex?

Answer 51

complex 6-layer structure of the cortex

Question 52

What is consistent and inconsistent in terms of the neocortex with mammals?

Answer 52

Different sizes, same general 6 layer structure within mammals

Question 53

What is the problem with increasing processing power in the cortex and how is it overcome?

Answer 53

- To increase intelligence need to increase processing power - Cortical neurons represent processing power = increased number of cortical neurons (thin layer at surface) - But: - Skull is confined structure, want to keep volume + mass to minimum - Big heads harder to protect than little ones - So: - We fold the cortex - Extensive folding in humans and dolphins - Gives bigger surface area without increasing the volume of head

Question 54

What is the top and the bottom of the fold in the cortex called?

Answer 54

- Top of fold called a gyrus (the peak) | - Bottom of fold called a sulcus (the trough)

Question 55

What is the frontal cortical love concerned with?

Answer 55

- voluntary actions, motor actions, speech control and emotion  Somatomotor cortex deals with motor information

Question 56

What is the parietal cortical lobe concerned with?

Answer 56

- deals with sensory information and language |  Somatosensory cortex – sensory information

Question 57

What is the occipital cortical lobe concerned with?

Answer 57

involved in processing visual information

Question 58

What is the temporal cortical lobe concerned with?

Answer 58

memory, sensory and language function

Question 59

Why are the somatomotor cortex and somatosensory cortex very important?

Answer 59

they control and receive information to and from particular parts of the body

Question 60

What does decussation mean?

Answer 60

'to become crossed'

Question 61

What does it mean that in the mammalian nervous system we see contralateral motor and sensory pathways?

Answer 61

the right side of the brain controls and receives sensory signals from the left side of the body and vice versa.

Question 62

Why do we see contralateral motor and sensory pathways?

Answer 62

Because the motor pathways leading from the cortex to the spinal cord and the sensory pathways from the spinal cord to the cortex decussate at the level of the medulla

Question 63

What is a consequence of the decussation of the mammalian nervous system?

Answer 63

that an injury or stroke on the right side of the brain will produce paralysis or weakness on the left side of the body.