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Flashcards in The Human Brain Deck (24):
1

3 main components of the CNS

- Neuron
- Glia cells
- Vasculature

2

Neuron

• A neuron is the basic signaling unit of the nervous system and which supports cognition
• Each neuron receives and combines multiple inputs to determine whether to transmit an action potential to the next target in the network
○ Axons (connecting fiber) send signals (axon terminals: at end of neuron)
○ Dendrites receive signals
○ Schwann cells: make myelin
- Myelin sheath : insulating fatty layer that speeds transmission

3

Glia cells

Provide support functions both chemically and structurally
• There are equal numbers of glia and neurons but different glia/neuron ratios in different structures in the human brain
○ Cerebellum: 0.23
○ Grey matter of cerebral cortex: 1.48
○ Rest of brain 11.35

• Main types of glia
○ Astrocytes: form the blood-brain barrier
○ Oligodendrocytes & Schwann cells - myelin production
○ Microglia : remove foreign & damaged cells

4

Vasculature

the arrangement of blood vessels which take blood to and away from the brain

5

Classification of neurons by shape

○ Unipolar: common in inverterbrate NS

○ Bipolar: found in some sensory systems incl the retina & olfactory system

○ Pseudounipolar: convey information from receptors in joints, muscles, and skin in the central nervous system

Multipolar: most neurons

6

Functional classification of neurons

○ Afferent (sensory) neurons: convey information from tissues and organs into the central nervous system

○ Efferent (motor) neurons transmit signals from the central nervous system to the effector cells.

Interneurons(association neurons) connect neurons within specific regions of the central nervous system.

7

Neurotransmitters

chemicals such as acethylcholine, serotinin, histamine, dopamine or oxytocin responsible for sending nerve signals across a synapse between 2 neurons (into the synaptic cleft)

8

How are neurotransmitters removed after they are released

○ Are removed after released by either 3 processes:
1. Active reuptake back into the presynaptic terminal
2. By the enzymatic breakdown of the chemical in the synaptic cleft
3. By diffusion, and away from the region of the synapse

9

Action potential

A sudden change (depolarization & repolarization) in the electrical properties of the neuron membrane in an axon
○ Consists of a no of phases

10

Graded potential

○ Some neurons do not generate action potentials, but instead generate a graded electrical signal, which in turn causes graded neurotransmitter release.

Such non-spiking neurons tend to be sensory neurons or interneurons, because they cannot carry signals long distances

11

Response rate

• Neurons code information in terms of a response rate, which is also called the spiking rate
○ Information is carried in the response rate of neurons
○ Different neurons respond in different situations, which shows the functional specialization of brain regions
- Neurons responding to similar types of information tend to be grouped together
○ The input and output of a neuron determines the type of information that neuron encodes

12

Synaptogenesis

The formation of synapses between neurons (creation of new synapses)
○ New synapses are also formed during learning and synaptic repair

13

Pruning

Refers to the elimination of synapses to increase the efficiency of neuronal transmissions
○ Grey matter volume declines from age 4-20

14

Neurogenesis

Refers to the formation of new neurons, this occurs throughout life

15

Gross organization of the brain

• Neurons group together to form
○ Grey matter: areas rich in neuronal cell bodies which are arranged in layers to form a sheet of tissue
○ White matter: bundle of axons and glial cells forming tracts interconnecting the brain

• The brain consists of highly convoluted sheets of grey matter (cortex) on top of white matter, underneath which lies another collection of grey matter:
○ Basal ganglia
○ Limbic system (hippocampus, amygdala & septum)
○ Diencephalon: thalamus & hypothalamus

• The cortex is composed of several layers (6) : thickness ranges from 1.5mm to 4.5mm
Most recent models of the brain show 210 cortical and 36 subcortical subregions

16

Sulci and fissures

• The sulci and fissures are both grooves in the cortex but they are differentiated by size
○ A sulcus is a shallower groove that surrounds a gyrus
- A fissure is a large furrow that divides the brain into lobes and also into the 2 hemispheres ( the longitudinal fissure)

17

The Forebrain

Made up of the:

• The Cerebral cortex: the outer layer of the cerebral hemispheres
○ Its functions include the processing of information, thinking and planning

• The basal ganglia are crucial to the function of the motor system

• The limbic system is involved in learning, emotions and motivation
- It includes the hippocampus, amygdala & septum

• The thalamus: is the primary relay station for sensory information coming into the brain

- The hypothalamus controls the endocrine system and the autonomic nervous system (body temperature, appetite and thirst regulation)

18

The Midbrain

• The reticular activating system (RAS) is important in controlling consciousness: (sleep, arousal), attention, cardiorespiratory function and movement
○ It extends into the hindbrain
- Other structures involved in vision, hearing and controlling movement

19

The Hindbrain

• The cerebellum is essential to balance & coordination of muscles (dexterity and smooth coordination of movement)

• The pons is involved in consciousness

- The medulla oblongata regulates vital functions and is involved in cardiorespiratory function, digestion and swallowing

20

The cerebral cortex (cerebrum)

• The cerebral cortex (cerebrum) is the largest part of the brain associated with higher brain function such as thought and action. It is further divided into 4 sections called lobes:

○ Frontal lobe
○ Parietal lobe
○ Occipital lobe
- Temporal lobe

21

The frontal lobe

- Memory
- Decision Making
- Reasoning
- Emotion regulation
- Personality
- Motor control
- Language

22

The Parietal lobe

- Senses and integrates sensation
- Spatial awareness and perception
- Proprioception (awareness of where parts of our bodies are)

23

The Occipital lobe

- Processing, integration and interpretation of VISION

24

The Temporal lobe

- Hearing
- Organization & Comprehension of language
- Memory & Memory formation