Topography Of The Brain And Meninges

Question 1

What tissue is the anterior pituitary derived from

Answer 1

The oral ectoderm, Rathke’s pouch, part of the developing hard palate in the foetus. Rathke’s pouch eventually loses connection with the pharynx giving rise to the anterior pituitary. Anterior pituitary formed from upgrowth from the oral ectoderm of primitive oral cavity called Rathke’s pouch.

Question 2

What is the posterior pituitary derived from

Answer 2

Nervous tissue
Has it embryological origins in nervous tissue. It’s formed from a downgrowth of the diencephalon that forms floor of third ventricle

Question 3

Differences between posterior and anterior pituitary

Answer 3

Posterior looks very different to anterior, it contains non-myelinated axons which are the neurosecretory cells. The cell bodies of these cells are located in the hypothalamus. Anterior pituitary secretes five different types of hormone, posterior secrets two
Anterior contains acidophils and basophils which can seen by stains theirs subtypes cant be seen
Capillaries in gland are fenestrated to enable passage of hormones from secretory cells into bloodstream

Question 4

Factors responsible for regulating hormone release from pituitary

Answer 4

Hypothalamus sends signals to pituitary to release or inhibit pituitary hormone production
Theres three mechanisms by which endocrine glands are stimulated to synthesise and release hormones: humoral stimuli (changes in extracellular fluids such as blood or ion concentration in blood), hormonal stimuli and neural stimuli

Question 5

Embryological origin of brain

Answer 5

Adult brain develops from the neural tube in 2 key stages
In first stage the neural tube differentiates to give rise to 3 distinct primary vesicles: the forebrain (prosencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon)
In second stage the forebrain and hindbrain each differentiate into 2 further secondary vesicles while midbrain remains unchanged this results in 5 secondary vesicles of embryonic brain which then develop progressively into adult brain

Question 6

What are the five secondary vesicles of brain

Answer 6

Telencephalon— cerebrum, lateral ventricles
Diencephalon — thalamus, hypothalamus, epithalamus, retina, third ventricle
Mesencephalon- midbrain, cerebral aqueduct
Metencephalon-pons- 4th ventricle
Myelencephalon- medulla oblongata- 4th ventricle

Question 7

What are the meninges of the brain

Answer 7

Three layers of membranes
Protect the brain and spinal cord
Dura mater, arachnoid, pia mater
Form boundary between CNS and PNS

Question 8

What is the enteric nervous system

Answer 8

A network of neurones found wholly within the gastrointestinal tract working to regulate its actions under the influence of both parasympathetic and sympathetic subdivisions of the ANS

Question 9

What is the central sulcus

Answer 9

Divides frontal lobe from parietal lobe

Question 10

What are sulci

Answer 10

A sulcus is a fissure or groove

Question 11

What are gyri

Answer 11

A gyrus is a ridge on surface of brain

Question 12

What’s the parieto-occipital sulcus

Answer 12

Divides parietal lobe from occipital lobe

Question 13

What’s the lateral fissure/sulcus

Answer 13

Divides temporal lobe from rest

Question 14

Frontal lobe

Answer 14

Function: planning and commanding voluntary movements
Landmark: central sulcus, pre central gyrus and lateral fissure

Question 15

Parietal lobe

Answer 15

Function: sensation and perception, integration and interpretation of sensory info primarily with visual field
Landmark: between frontal and occipital lobe above temporal lobe on each cerebral hemisphere, anterior border is the central sulcus, posterior border is parieto-occipital sulcus

Question 16

Temporal lobe

Answer 16

Function: hearing, sensory aspects of speech and memory
Landmark: middle cranial fossa, next to temporal bone, lateral sulcus, collateral sulcus

Question 17

Occipital lobe

Answer 17

Function: visual processing area, visuospatial processing, distance and depth perception, colour determination, object and face recognition & memory formation
Landmark: posterior to parietal lobe and temporal lobe, imaginary plane in line with parieto-occipital sulcus

Question 18

Limbic lobe

Answer 18

Functions: modulation of emotions, visceral functions, autonomic functions, hormonal functions, learning and memory
Landmark: borders corpus callosum on medial aspect of each hemisphere, surrounds rim of ventricles to brain

Question 19

What is the corpus callosum

Answer 19

Large bundle of myelinated nerve fibres that connect the two brain hemispheres together permitting the communication between right and left sides of brain

Question 20

Insular lobe

Answer 20

Function: associated with processing and integration of various types info including taste, visceral sensation, pain and vestibular
Landmark: deep within lateral sulcus, 5th lobe of brain, not visible from outside

Question 21

What are the 4 subdivisions of the diencephalon

Answer 21

Thalamus, hypothalamus, epithalamus, subthalamus

Question 22

Thalamus

Answer 22

Function: major relaying centre of the brain, its nuclei act as ‘switchboards’ controlling sensory inputs and motor outputs
Anatomical relations: located on either side of 3rd ventricle

Question 23

Hypothalamus

Answer 23

Function: maintain homeostasis in body, energy consumption, hunger, awareness
Relations: below thalamus and anterior to thalamus

Question 24

Epithalamus

Answer 24

Functions: to connect limbic system to other parts of brain, synthesises melatonin and enzymes sensitive to daylight
Relations: above pineal gland and posterior to thalamus

Question 25

What is the limbic system

Answer 25

Part of brain involved in behavioural and emotional responses

Question 26

Subthalamus

Answer 26

Functions: the subthalamic nucleus plays a vital role in the modulation of movement, helps to modulate movement through indirect pathway of basal ganglia with other compartments of basal ganglia
Relations: between thalamus and midbrain

Question 27

What makes up the brainstem

Answer 27

Midbrain, pons and medulla oblongata

Question 28

Functions of the brainstem

Answer 28

Houses motor and sensory pathways that act as ‘motorways’ between cerebral cortex and spinal cord
Regulates some of brains basic functions that sustain life such as breathing and regulation of heart rate

Question 29

How does cerebrospinal fluid help to protect brain against injury

Answer 29

Acts as a shock absorber, cushioning brain and skull and spinal cord
Allows brain and spinal cord to become buoyant reducing effective weight of brain
Fluid also removes waste products from brain and helps CNS work

Question 30

What is meant by hydrocephalus

Answer 30

Build up of fluid in the brain, excess fluid puts pressure on the brain which can damage it
It can occur by an imbalance between how much CSF is produced and how much is absorbed by bloodstream

Question 31

Layers of scalp

Answer 31

Skin
Connective tissue
Aponeurosis-thin sheath of connective tissue
Loose connective tissue
Periosteum-dense layer of vascular connective tissue

Question 32

Dura mater

Answer 32

First layer, cranial dura mater has 2 layers called lamellae, a superficial layer (periosteal layer) and meningeal layer

Question 33

Arachnoid

Answer 33

Vascular, blood supply
Only layer with blood supply, fluid

Question 34

Pia mater

Answer 34

Can’t see normally, innermost layer, composed of delicate connective tissue