OCR Biology A level - Brain

Skull

Bones called cranium which protect delicate nervous tissue.

Meninges

• Membranes which surround the central nervous system.

• Secrete Cerebrospinal fluid + offer protection.

Cerebro-spinal fluid

• Secreted by meninges, provides protection via absorbing mechanical shocks.

• Provides nutrients and oxygen to brain cells.

Ventricles

Spaces within brain filled with CSF.

Corpus Callosum

Connects left and right cerebral hemispheres, allowing the 2 sides of the cerebrum to communicate.

Structure of Cerebrum

• Largest Brain Region: Makes up 80% of brain’s mass

• Two Hemispheres, each with 4 lobes

• Left hemisphere controls the right side of the body, and vice versa

• Corpus Callosum: Nerve band connecting the two hemispheres

• Cerebral Cortex: Outermost layer, 2-4 mm thick, made of cell bodies, highly folded and convoluted, increasing surface area for complex processing

Functions of Cerebrum

• Coord. voluntary actions, vision, speech, problem solving,

  hearing, decision making, intelligence, reasoning, judgement,

  conscious thought, emotional response, fact memory.

Structure of Cerebral Cortex

Made of grey matter (non-myelinated) and subdivided into areas responsible for specific functions:

• Sensory area

• Association area

• Motor area

Structure of Cerebellum

• Underneath the cerebrum containing ½ of all brain neurones.

• Connected to the cerebrum by the pons.

• Involves a high degree of rapid communication.

Functions of Cerebellum

• Coord. involuntary movement and balance (it does not initiate it)

• Fine movement/balance/posture = riding a bike

• Judging positions of objects = limbs in sport

• Tensioning muscles = using tools or instruments

• Antagonistic muscles = walking/running

Hypothalamus structure

• Middle of lower side of the brain. Above and connected to pituitary gland.

• Main control of the ANS (2 centres: sympathetic and parasympathetic)

• Controls homeotic mechanisms of the body. Endocrine function.

• Contains own sensory receptors. Acts via negative feedback.

Hypothalamus functions

• Temperature Regulation

• Osmoregulation

• Digestive system activity

• Endocrine function

Pituitary gland structure

Pea sized endocrine gland.

Acts in conjunction with the hypothalamus.

2 lobes below the hypothalamus attached to pituitary stalk.

Pituitary gland function

Posterior Pituitary Gland

Linked to hypothalamus by neurosecretory cells.

ADH made in hypothalamus 🡪 neurosecretory cells 🡪 pituitary

gland 🡪 enters the blood.

It stores and secretes. E.g. ADH, oxytocin

Anterior Pituitary Gland

Makes own hormones 🡪 directly into the blood in response to

releasing factors from the hypothalamus.

Stress response, growth, FSH, lactation, reproduction.

Travels only short distances.

Medulla Oblongata structure

Coordination centre of the ANS.

Found at the base of the brain joining to the spinal cord.

Physiological processes.

Medulla Oblongata function

Controls involuntary actions

Cardiac centre

Vasomotor centre

Respiratory centre