1 Functions of the cerebrum, hypothalamus, cerebellum and medulla oblongata Symptoms and possible causes of Alzheimer’s disease Sympathetic and parasympathetic systems Gross structure of the human brain Organisation of the nervous system Digestion, heart action, pupil diameter Investigating the human brain Review and test BACK TO MAIN A2 BIOLOGY MENU

2 The Organisation of the Nervous System Types of cells Neurones Glial cells Transmit nerve impulses Help with ionic balance and nutrient supply to the neurones e.g. Schwann cells Organisation There are 2 main parts to the nervous system: The Central Nervous System: brain and spinal cord The Peripheral Nervous System: the neurones that lie beyond the brain and spinal cord

3 The Organisation of the Nervous System The central nervous system - CNS Most neurones in the CNS are intermediate neurones, often each with thousands of synaptic connections These synaptic connections are of 2 types: Excitatory – action potentials in the nerve depolarise the post synaptic membrane of the nerve on the other side of the synapse Inhibitory – action potentials in the nerve hyperpolarise the post synaptic membrane of the nerve on the other side of the synapse There are about 200 x neurones in the brain and the mix of inhibitory and excitatory synapses provides an almost infinite framework for patterns of nervous activity

4 The Organisation of the Nervous System The spinal cord (SC) runs through the neural arches of the vertebrae and in its centre is a canal containing cerebrospinal fluid. The brain is a highly specialised area of the SC. See later The spinal cord The brain and spinal cord are surrounded by 3 membranes called the meninges The meninges secrete cerebrospinal fluid. The fluid supplies oxygen and nutrients and acts as a shock absorber The meninges Butterfly shaped area of unmyelinated neurones (grey) Myelinated neurones (white) Canal

5 dendrites nucleus Node of Ranvier myelin sheath synapse axon cell body The Organisation of the Nervous System Types of cells NeuronesTransmit nerve impulses

6 In the knee jerk reflex, the lower leg swings forward quickly when an area just below the knee is tapped. In order for this reflex to occur, a message travels through a sensory neuron to the spinal cord, where an interneuron carries it to a motor neuron, which sends the information to the leg muscle and causes the movement. The Organisation of the Nervous System The peripheral nervous system The cell bodies of sensory neurones are lie just outside the spinal cord in the dorsal root ganglion (a group of nerve cell bodies) The cell bodies of motor neurones are in the spinal cord Axons and dendrites are arranged in bundles called nerves CHECK IT OUT A typical somatic NS reflex arc

7 The Organisation of the Nervous System MYELIN SHEATH AXON TS Nerve containing 100s of axons and dendrons x100 Nearly all the nerves shown are myelinated but a few are non- myelinated BACK

8 CENTRAL NERVOUS SYSTEM (CNS) PERIPHERAL NERVOUS SYSTEM (PNS) NERVOUS SYSTEM SOMATIC NERVOUS SYSTEM (voluntary) AUTONOMIC NERVOUS SYSTEM (involuntary) SENSORY AND MOTOR NEURONES TO / FROM SKELETAL MUSCLE MOTOR NEURONES TO INTERNAL ORGANS SYMPATHETIC NERVOUS SYSTEM (involuntary) PARASYMPATHETIC NERVOUS SYSTEM (involuntary) CONTROLS ORGANS IN TIMES OR STRESS CONTROLS ORGANS WHEN BODY IS AT REST The Organisation of the Nervous System BRAIN AND SPINAL CORD PERIPHERAL NS

9 PUPILS SALIVARY GLANDS HEART BRONCHI LIVER STOMACH/ SMALL INTESTINE ADRENAL GLAND / KIDNEYS LARGE INTESTINE BLADDER / GENITALS The Organisation of the Nervous System The sympathetic nervous system Series of ganglia The cell bodies of its motor neurones lie in ganglia outside the spinal cord From these ganglia sympathetic motor axons pass to all organs of the body, eventually synapsing with muscles, e.g. cardiac, smooth. The transmitter liberated at these synapses is usually nor adrenaline – it stimulates organ activity Ach is released at motor endings in sweat glands, erector muscles and some blood vessels. It too causes stimulation. SNS functions are FIGHT OR FLIGHT

10 The Organisation of the Nervous System EYE SALIVARY GLANDS BRONCHI HEART STOMACH PYLORIC SPHINCTER PANCREAS LARGE INTESTINE, ANAL SPHINCTER GENITALS BLADDER The Parasympathetic Nervous System The nerve pathways all begin in the brain, or at the top or bottom of the SC The neurones keep going ‘till right inside the organ. Here they synapse with a motor neurone The transmitter liberated at these synapses is acetylcholine and this has an inhibitory effect on the organ Many parasympathetic axons are part of the vagus nerve. PNS functions are REST AND DIGEST

11 Cranial parasympathetic fibres Sacral parasympathetic fibres Sympathetic fibres Ach NA Ach GANGLION The Organisation of the Nervous System VISCERAL EFFECTOR Preganglionic neurone Motor neurone Layout of motor pathways in the autonomic nervous system

12 Organ Effect of sympathetic stimulation Effect of parasympathetic stimulation Heart Eye Digestive system Skin pupil ciliary muscles glands sphincter muscles liver sweat glands erector muscles arterioles Increase rate and force of contraction Dilates Relax – lens thinner for distant vision Little or no effect Contraction Release of glucose into blood Increases sweating Contract, making hairs stand on end vasoconstriction Reduces rate and force of contraction Constricts Contract – lens thicker for near vision Stimulates secretion Relaxation Small increase in glycogen production Little effect, except to increase sweating on palms of hands No effect Some sympathetic and parasympathetic effects The Organisation of the Nervous System

13 Effect on the digestive system Sympathetic and parasympathetic action PARASYMATHETIC STIMULATES DIGESTION Sphincter muscles relax Peristaltic muscles contract more frequently Salivary glands produce more saliva Gastric glands secrete more juice SYMATHETIC WEAKLY SUPPRESSES DIGESTION Sphincter muscles close Reduces peristalsis Reduced blood supply to gastric and salivary glands

14 Sympathetic and parasympathetic action PARASYMPATHETIC REDUCES THE RATE AND FORCE OF CONTRACTION SYMPATHETIC INCREASES THE RATE AND FORCE OF CONTRACTION Ach NA Ach release from the vagus nerveNA release from sympathetic nerves The action of the heart

15 Pupil dilation and constriction Sympathetic and parasympathetic action

16 Pupil dilation and constriction Sympathetic and parasympathetic action CLICK TO CONSTRICT PUPIL DILATED The pupil is the dark space in the centre of the iris The iris contains circular and radial muscles and their activity can change pupil diameter The SNS is stimulating the radial muscles to contract, widening the pupil. Causes: Dim light Excitement Fear radial circular

17 Pupil dilation and constriction Sympathetic and parasympathetic action CLICK TO DILATE PUPIL CONSTRICTED The pupil is the dark space in the centre of the iris The iris contains circular and radial muscles and their activity can change pupil diameter The PSNS is stimulating the circular muscles to contract, narrowing the pupil diameter Cause: Very bright light radial circular

18 The study of the brain - introduction The Brain Difficulties arise because of the enormous number of cells and the huge numbers of connections Thus research often focuses on the function of groups of cells and how they connect to other groups Post-mortem examination of brain tissue from patients with mental disorders was for a long time the only way that brain function could be studied THE HUMAN BRAIN Pierre Broca (France, 1861) for example studied the brain of a patient who could not speak or write but could understand language that he read or heard He found that a small area at the front left side was damaged. Discovery of similar damage in other patients led to this being called Broca’s area. Broca’s area responsible for the production of language

19 The study of the brain – methods used The Brain Studies of the brains of people with brain illnesses THE HUMAN BRAIN Investigating areas of brain activity in healthy people Studying the effect of particular drugs on the brain. CAT scanning PET scanning MRI scanning Computer assisted tomography Positron emission tomography Magnetic resonance imaging before or after death, either by using post-mortem brain slices or new scanning methods on living patients. using new scanning techniques Trials with various molecules have provided much information about the structures and functions of molecules found in normal brains

20 The Brain - Structure EXTERNAL STRUCTURE CEREBRUM WITH FOLDED OUTER LAYER CALLED CEREBRAL CORTEX FRONTAL LOBE TEMPORAL LOBE PARIETAL LOBE OCCIPITAL LOBE CEREBELLUM MEDULLA OBLONGATA

21 The Brain - Structure VERTICAL SECTION THROUGH THE HUMAN BRAIN FRONTAL LOBE VENTRICLES CONTAINING CEREBROSPINAL FLUID - CSF PARIETAL LOBE OCCIPITAL LOBE CEREBELLUM MEDULLA OBLONGATA SPINAL CORD PITUITARY GLAND THALAMUS HYPOTHALAMUS

22 The Brain - Function THE MAJOR PARTS OF THE BRAIN The cerebrum contains the right and left cerebral hemispheres linked by the corpus callosum The surface of each cerebral hemisphere is covered by a highly folded tissue called the cerebral cortex Lobes in the cerebral cortex: frontal, parietal, temporal, occipital. The thalamus and hypothalamus lie below the cerebrum. The hypothalamus is closely associated with the pituitary gland Part of brainFunction Cerebrum Hypothalamus Cerebellum Medulla oblongata Thinking, language, planning, emotions, memory Control of the autonomic nervous system and some endocrine glands Control and coordination of movement and posture Control of breathing movements, heart rate, action of smooth muscle in the gut

23 Both cerebral hemispheres receive sensory information from the eyes, ears, skin etc. The Brain - Function Areas first receiving this information are called primary sensory areas The Cerebrum Areas which then process and integrate this information are called association areas. Broca’s area Association areas Primary auditory area Primary visual cortex There are 3 main association areas making up a large part of the cortex. They involve co-ordination such as body position analysis, planning actions and movements, and also creating emotions and memory

24 PET scanning of the brain shows that different regions are involved in different stages of a task. E.g. communicating with words The Brain - Function The Cerebrum Looking at words Listening to words speaking words Thinking of words In the mid 1800s Paul Broca discovered that 1 small area of the brain was involved in the production of language, speech or writing In 1876 Carl Wernicke reported a different are responsible for the understanding of language Although the right and left cerebral hemispheres communicate constantly through the corpus callosum, there is an asymmetrical distribution of sites for language and 3D processing

25 Dr Paul Broca Carl Wernicke

26 The Brain - Function The right and left cerebral hemispheres

27 The Brain - Function right thalamus left thalamus cerebellum hypothalamus cerebral cortex Functions of the hypothalamus

28 The Brain - Function HYPOTHALAMUS ANTERIOR PITUITARY POSTERIOR PITUITARY Nerve cells in the hypothalamus synthesise oxytocin and antidiuretic hormone (ADH). These travel along axons to the posterior pituitary. They are released from nerve endings into the blood when the nerves are active. Pituitary Hormones Nerve cells in the hypothalamus synthesise and release hormones into the blood stream. This is called neurosecretion. The hormones (called releasing hormones) travel to the anterior pituitary where they stimulate further hormone release into the blood (see next table)

29 The Brain - Function Action of hypothalamus Effect on PituitaryResult Secretion of thyrotropin releasing hormone Secretion of growth hormone releasing hormone Secretion of gonadotrophin releasing hormone Production of antidiuretic hormone (ADH) Production of oxytocin Release of thyroid stimulating hormone from the anterior pituitary Release of growth hormone from the anterior pituitary Release of LH and FSH hormone from the anterior pituitary ADH is released from nerve endings in the posterior pituitary Oxytocin is released from nerve endings in the posterior pituitary Release of thyroxine from thyroid gland which increases metabolic rate Water retention by the kidney FSH: Follicle growth in ovaries. Sperm production in the testes. LH: Ovulation and secretion of oestrogen progesterone and testosterone. Uterus contraction during birth. Milk ejection during breast feeding Growth of cells and tissues Pituitary Hormones

30 Functions of the cerebellum Coordination of movement and posture Does this by smoothing the action of movements initiated by the motor cortex Involved in coordinated task learning – e.g. riding a bicycle, catching a ball The Brain - Function Medulla oblongata

31 Medulla oblongata Functions of medulla oblongata The Brain - Function Breathing: Controls diaphragm and intercostals via the vagus nerve If blood CO 2 changes the medulla can modify the speed and depth of breathing Heart rate and blood pressure: Sympathetic and parasympathetic (vagus) nerves link the medulla to the SAN CO 2 levels are monitored by receptors in the medulla itself, and also by receptors in the walls of the carotid arteries and aorta. Baroreceptors (pressure receptors) in the carotid arteries and CO 2 receptors monitor levels and send information to the medulla High blood pressure or low CO2. Response: Vagus nerve causes the SAN to pulse more slowly Low blood pressure or high CO2. Response: Sympathetic nerves cause the SAN to pulse faster

32 ( from the front). The Brain - Function Shrinkage of brain tissue. Ventricles enlarge. short-term memory begins to decline ability to perform routine tasks also declines. Emotional outbursts may occur and language is impaired. Progressively more nerve cells die with subsequent behaviour changes, such as wandering and agitation. The ability to recognize faces and to communicate is completely lost in the final stages. Patients lose bowel and bladder control, and eventually need constant care. The average length of time from diagnosis to death is 4 to 8 years, but can take 20 Alois Alzheimer Alzheimer’s disease First recorded by Alzheimer after studying the brain of a woman who had died after suffering dementia in 1906.

33 Alzheimer’s disease and amyloid plaque formation The Brain - Function In Alzheimer's some of the neurones have bundles of fibres in them, called ‘tangles’. Between the neurones there are dark-staining deposits called plaques The tangles in the neurones are made of a protein called tau. The plaques contain a peptide called beta amyloid, Aβ All cell membranes contain a larger protein called amyloid precursor protein or APP. APP to Aβ conversion is part of the normal activity of the cell membrane, but the resulting Aβ is removed by the tissue fluid. Abnormal metabolism of APP may be the cause of some types of Alzheimer’s

34 The Brain - Function Ageing. Less than 1 in 1000 people 65 has! A small proportion of sufferers have a genetic (familial) form A varied and active life may help avoid Alzheimer’s. Severe blows to the head (especially in the over 50s) may increase the chance of developing the disease Smoking and high cholesterol may also be risk factors for Alzheimer’s Future therapy? A vaccine to break down the β amyloid plaques? Trials in mice An inhibitor of the membrane enzyme that breaks down APP into Aβ? Risk factors Alzheimer’s

35 Describe the organisation of the nervous system with reference to the central and peripheral systems Outline the organisation of the autonomic nervous system into a parasympathetic and a sympathetic system Outline the roles of the autonomic nervous system in controlling the digestive system, heart action and the size of the pupil in the eye Outline the functions of the cerebrum, hypothalamus, cerebellum and medulla oblongata Describe the symptoms and possible causes of Alzheimer’s disease as an example of brain malfunction. Describe the gross structure of the human brain WHAT YOU SHOULD KNOW AT THE END OF THIS UNIT TEST QUESTIONS

36 Q2 Q1 Q3 Q5 Q10 Q11 TOTAL /23 Name the 2 major parts of the nervous system 2 What are the 2 divisions of the peripheral nervous system? 2 Give 2 features of the parasympathetic stimulation of digestion 2 For what reasons have Paul Broca and Carl Wernike become famous? 2 Give the 2 most obvious anatomical symptoms of Alzheimer’s disease 2 Outline the effect of the PSNS on light entry into the eye. 2 Q4 Give 2 features of the sympathetic control of the heart beat 2 Q6 Name 2 cerebrum functions listed in the table you were given. 2 Q7 What is neurosecretion? 3 Q8 What are the main function of the cerebellum. Give 1 example of this function. 2 Q9 The medulla oblongata controls breathing. Name 2 places where CO2 receptors are found 2 The central and peripheral nervous systems The somatic and the autonomic nervous systems Salivary secretion increases, peristaltic increase, sphincters relax, gastric glands secrete more ‘Discovered’ centres for: Production of speech, writing. Understanding of language. Shrinkage of brain tissue, enlargement of the ventricles, amyloid plaque formation Stimulates circular muscles to contract, narrowing the pupil diameter. Increased force and increased rate of contraction Thinking, planning, language, emotions, memory Synthesis and release into the blood of hormones by nerve sells in the hypothalamus Coordination / smoothing of movement and posture. e.g. flying / riding a bike In the medulla, in the walls of the carotid arteries and aorta. Name ________________